Dual booting Windows 7 and Windows 10

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Calavera
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Dual booting Windows 7 and Windows 10

Post by Calavera »

I currently have Windows 7 installed but soon plan on also installing Windows 10 to try out some Windows 10 exclusive games. I'm pretty sure I know how to do it but figured I'd ask here just to double check. The drive I have Windows 7 installed on is an SSD with just 1 partition, so I plan on shrinking that partition down. I have a secondary HD where all games and programs are installed so I only use the main drive for OS files. I've read the minimum space requirement for 10 is 20gb, so I figure I should allocate a little more than that. I was thinking 30-35gb? Will that be sufficient? After I create the new partition I'm guessing all I do is run the Windows 10 installer as usual the once it is finishing I will get a screen to pick from 7 or 10 after a reboot?

I'm pretty sure all the information is correct, but it never hurts to double check. Thanks!
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melancholy
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Re: Dual booting Windows 7 and Windows 10

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I believe this only works if you install Windows 10 first. Reason is because Windows 10 uses an entirely different boot method that will make the Win 7 portion unbootable. Of course the best method would be to just have the two OS on two different drives. That way you just choose what HDD you want to boot during startup and you don’t have to worry about an update on one bricking the boot files of another. A 120GB is cheap nowadays (Best Buy had one for $30 last week), just get one of those.

If you do go the partition route, expect Win 10 to constantly use up about 5-10 GB for caching updates. Anything less than a 30GB partition will likely prevent Windows from installing any service packs. If I were you, I’d do 40GB just to be safe.

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Calavera
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Re: Dual booting Windows 7 and Windows 10

Post by Calavera »

melancholy wrote:I believe this only works if you install Windows 10 first. Reason is because Windows 10 uses an entirely different boot method that will make the Win 7 portion unbootable. Of course the best method would be to just have the two OS on two different drives. That way you just choose what HDD you want to boot during startup and you don’t have to worry about an update on one bricking the boot files of another. A 120GB is cheap nowadays (Best Buy had one for $30 last week), just get one of those.

If you do go the partition route, expect Win 10 to constantly use up about 5-10 GB for caching updates. Anything less than a 30GB partition will likely prevent Windows from installing any service packs. If I were you, I’d do 40GB just to be safe.
Thanks for the information. I had thoughts of getting a cheap second drive but I thought eh if I can put it on the same drive then why not just do that. The possibility of one bricking the boot files of another through an update or something else is a good reason to just get a second drive. I went looking for the cheapest drive I could find and I found 160gb for $10!

https://www.ebay.com/itm/New-160GB-8MB- ... XQdm5Q-s7R

I know that seems way too cheap but the guy has sold almost 4,000 of this particular drive and has 100 percent feedback on ebay so he can't just be selling junk drives. For $10 I'll probably pick one up and see how it does.
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melancholy
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Re: Dual booting Windows 7 and Windows 10

Post by melancholy »

It’s weird that drive doesn’t have any brand on it. That guy is also selling official Seagate 160GB drives for only $4 more, I would go with that instead.

But whatever you do, having two separate drives is always the better option. And only have one drive plugged in at a time during each OS install. I’ve had times in the past where drive letters get messed up when the installer sees another Windows. Once both OS are installed, then plug both drives in and you’ll be good.

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Calavera
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Re: Dual booting Windows 7 and Windows 10

Post by Calavera »

melancholy wrote:It’s weird that drive doesn’t have any brand on it. That guy is also selling official Seagate 160GB drives for only $4 more, I would go with that instead.

But whatever you do, having two separate drives is always the better option. And only have one drive plugged in at a time during each OS install. I’ve had times in the past where drive letters get messed up when the installer sees another Windows. Once both OS are installed, then plug both drives in and you’ll be good.
Looks like the seller is also on newegg
https://www.newegg.com/Product/Product. ... 5AD3KE4385

It is even a bit cheaper on there $9.99 total vs $10.94

So you would recommend I only hook up the new drive when installing Windows 10, then afterwards hook the other drives back up and use the boot selector at the bios startup to select the OS and not even bother with any kind of menu system?
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melancholy
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Re: Dual booting Windows 7 and Windows 10

Post by melancholy »

Exactly. That way you are sure the two OS won’t try to conflict with each other. It’s not the most elegant, but it is the easiest way to dual boot.

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Calavera
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Re: Dual booting Windows 7 and Windows 10

Post by Calavera »

I've got both Windows 10 and 7 installed now and everything is working fine except for I have to do one extra step when switching between the two. When I went to install Windows 10 it told me that Windows couldn't be installed on that drive. I looked into it and found something about changing the sata controller mode would help. So I changed it from ACHI to IDE mode and then Windows 10 installed fine. Windows 7 won't boot if I leave it on IDE mode. So each time I want to switch to the other OS besides selecting the drive from the boot menu I have to also go into the bios and change the SATA controller mode.

It's not really a big deal as it only takes a few extra seconds to do, but just thought I'd mention it and see if anyone else ever had this happen. I wonder why Windows 10 wouldn't install with the SATA controller on ACHI?
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melancholy
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Re: Dual booting Windows 7 and Windows 10

Post by melancholy »

Dunno, never heard of that. But I searched and apparently there is a simple fix for it that doesn’t require a re-install.

https://triplescomputers.com/blog/uncat ... operation/

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Calavera
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Re: Dual booting Windows 7 and Windows 10

Post by Calavera »

I wasn't even going to post about this but I saw this old thread and figured why not post about it here.

Awhile ago I needed to backup files from a failing hard drive. Long story short the easiest way I could do it at the time was to use a different PC and install Windows 10 on to the new drive then hook the failing drive up as the secondary in that system.

When I put that new drive with the backed up files and the Win10 installation in my PC it boots from it by default. I have my Win10 installation on my M.2 drive but for some reason I am unable to select it as the default boot drive in the bios.

It really isn't a problem though. When I boot up my PC I just have to press F11 so the boot menu will come up and then select my M.2 drive and everything loads up fine. Maybe that extra Win10 install will come in handy someday if my main install won't boot or something.

So while it isn't really problem it is weird that I can't make my M.2 drive the default boot device in the BIOS. I should be able to make any damn drive I want the default. Even a floppy drive if I wanted.
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Re: Dual booting Windows 7 and Windows 10

Post by melancholy »

So with UEFI motherboards, booting works differently. Instead of booting to whatever drive you have on the list first, these motherboards look for a boot partition on all the drives and automatically boot to that first. If there are multiple drives with boot partitions, it usually chooses the first one it finds, and a lot of motherboards will load up the SATA ports before the PCI-E bus. Boot order in the BIOS is simply for when there is no boot partition on any drive and it falls back to a legacy mode of booting.

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