Wiping hard drive/restore from another pc?

I’m supposed to be fixing my father-in-law’s computer. He’s a porn junkie, and he’s got so many viruses and spyware on his desktop[sup]*[/sup] that I really think it’ll be quicker and easier to just format his hard drive and reinstall Windows 7 (seriously, he has over 1000 pieces of spyware, even with AVG and Spybot installed). I can’t find my restore disc, and I know he has no idea where his is. So here’s what I wonder:

Would it be easy to just link my pc to his via USB, and install his OS that way, or is there something easier? I have USB problems of my own (loose USB ports), so I’m not sure that I could make a copy of the OS to flash drive to use on his. Also, I wouldn’t know where to find the product code for him to use to restore full functionality. Of course, the USB ports being loose could make it difficult to keep the laptop and his desktop linked.

Any idea, computer-savvy people?

Is there a windows product key on a sticker on the tower case somewhere? That makes things a bit easier if so. If it has worn off or whatever, and his Windows install is legit otherwise, there are other ways to recover the key. I recommend method 2 here (because Hiren’s is very handy for all sorts of things) but method 1 will suffice.

Once you have the key, and you don’t have install media, follow the instructions here

http://www.pcworld.com/article/248995/how-to-install-windows-7-without-the-disc.html

You could see how far back the restore points go, but in cases like these I usually just nuke it and start over. Save all the drivers and personal stuff. I use DBAN. Just tell Dad to bite the bullet and buy a legal copy of Windows off Amazon for $100 or so. A lot of old farts literally just use their machine for Internet access. They have no interest in any other use, or the knowledge to implement it. If that’s the case, you can even just install Ubuntu and be done with the whole affair in half an hour with no expenditure. You wouldn’t even need to download Firefox—it’s already bundled with the OS.

And with Ubuntu, or any other Linux — although I rarely encourage non-linuxians to try Linux — any Windows malware he chooses to add to his collection just stays in Limbo impotent to attack his machine.