Need a bit of worldly advice

[xxWulfyxx]

Sorry this may be the wrong subforum to post this in...in fact none of them looked like the right ones. Anyway;

Back in October 2011 I bought a "Titan Spinosaur" Intel Core i5 2500K 3.30GHz @ 4.60GHz DDR3 Sandybridge System from OcUK - I still have the receipt etc
It came with an OEM version of Windows 7 Home Premium 64 bit pre-installed and subsequently to that I have upgraded (via online download) to Windows 8.1 Professional 64 bit...so I have no physical disks at all.

I now want to do a complete reformat, get rid of the chaff n' crap and take it back to Win 8.1 but without the disks I have no idea how to go about it. I could buy a copy of Win 7 64, they are relatively cheap nowadays, and then do the online download again (I hope) but I'm kind of thinking "why should I when I theoretically already have bought Win 7 with the PC?"

Can anyone suggest the best way to go about this?

 

[xxWulfyxx]

Go here, enter product key, and you should be gold: http://windows.microsoft.com/en-us/windows-8/upgrade-product-key-only

Ahh - brilliant! If I read that correctly then, I don't need to reformat or have the disks - I just type in my Win 8 product code and it will reformat and do everything online? I never knew it could do that - in the old days when I'd do a reformat I couldn't even get online until windows was fully installed!

And this will wipe everything? Even illicit handbag & shoe shopping websites, all references to Pokemon, any malware or whatever else dodgy stuff like Somalian bankers wishing to track soon-to-be-wealthy relatives that has possibly got on the PC?

 

[xxWulfyxx]

Thanks for all the information guys. I'm starting to back up all my photos and music - the rest I want I can just reinstall, nothing is really 'mission critical'.

One final question (I promise!) - what size USB do you think it will ask me for. I have an old small one (according to my wife!) but I can "borrow" one from work if I know the size.