Dban or not?

[Rjae]

I have bought a new computer (desktop) and want to use my old one to run a touchscreen monitor which needs windows 7.

My old computer has windows vista. I have a disc and verification key for windows 7.

My old computer is crushingly slow and full of crap.

Q1. If I nuke the whole computer with a dban disc will I be able to reinstall the OS windows 7 from disc?

Q2. Would it be a safer option to take as many programs as possible off in the 'program's and features' and leave vista alone will the windows 7 quarantine off the vista?

Q3 is there any way I can make it faster and unclogged if option 2 doesn't work. (Have taken it in to be serviced) and it came back the same)

I've taken off malwarebytes and S&D and ccleaner. And it just has a new copy of mcafee. Previously it had all the above (except mca fee) and free avg.

Tia

You don't need to remove anything from your old computer before installing Windows 7 (although you do need to make sure you've got backups of everything you need). Your Windows 7 installation disk will almost certainly offer you the choice of doing a clean install rather than an upgrade. A clean install will result in Windows 7 with no installed software (other than the stuff that is bundled with Windows 7) and no other files on the PC.

Thanks. I will do that today. I've got the photos and documents onto an external hard drive so fingers crossed for a clean install. Yesterday I did a factory system restore just to see what would happen and it behaved itself and left just the windows vista so the windows 7 should be too.