Dual boot windows advice please

[ALS57]

Hi All

I have a work desktop PC running Windows 7 on a 500gb SSD. I need to keep Windows 7 to run some old textile design software and I can't risk messing up that software installation, it was very expensive.
In order to run Windows 11 on the same PC I'm about to install a new 1TB SSD and install Windows 11 on that new drive which hopefully will give me a dual boot option on start up. So the plan is, Windows 7 left alone on the old 500Gb SSD and add Windows 11 on the new 1Tb drive.

The questions I have are:
When formating the new 1tb SSD for Windows 11, what drive letter do I assign to that new drive? Will Windows 11 and Windows 7 automatically switch their respective drives to "C" from the dual boot screen?
Will I now have 2 sets of user accounts, one for each OS?
I assume I need to buy a new product key for for Windows 11?
It's crucial i can still run that textile software on Windows 7. Will the Windows 11 on it's new drive intefere with the Windows 7 drive in any way?

I would appreciate any advice please

Thanks

Al

 

[ALS57]

Thanks Orcvader
If i unplug the drive with 7 in it while installing 11 will I still get this screen option when I boot the PC?

 

[ALS57]

Thanks Darael, will do the backup.
The textile software just won't run on Windows 8 or 10 unless you pay for the later versions. The Windows 7 version I bought was £6000 about ten years ago! it also needs a USB security key dongle to work

 

[ALS57]

Thanks all for the input, much appreciated