I can’t imagine it’s going to take less time to buy and setup a new PC than it is to wipe it and start again. Then there’s the issue of that being rather wasteful to say the least!
Buy an OEM copy of W7. Back up your data on two external hard drives, wipe the Vista install completely and then reinstall Windows. I would not connect your data-drives until you have antivirus and all the patches installed.
You could also use W10, it might well be better, but probably more expensive than W7. You can also do an upgrade to 10 using a W7 product key, which might be best of all.
I strongly advise against dodgy copies of Windows, as they probably come with security holes or spyware in.