Windows disk help

So my friend is having problems with his computer.
We think he is missing a windows file and he has the windows disk but we don't know what option to click when it opens up to repair it.
We seriously need help as soon as passably.
he has three disks,
1.) Windows XP home edition
2.) Another Windows XP home edition
3.) Re installation CD, Microsoft Windows XP professional including service pack 1A (by dell)

When we use one or two all these options come up and were not sure what to do.
We haven't put three in because we're afraid that it will wipe his hard drive or something. If three is the right one to repair the files or something will it wipe his hard drive?
Please help!!!

We think

Screw with installation CDs after you KNOW what's wrong.

So. What's wrong?

Screw with installation CDs after you KNOW what's wrong.

So. What's wrong?

It's either a virus or a missing windows file.
The other day he was deleting files and cleaning up his computer and then all these problems started.
his computer started going SUPER SUPER slow and not operating right and crashing like crazy. ( by crashing I mean internet and a lot of un-responding programs, downloads going at like 10 kb per second or lower. etc)

Same problem with my computer - it's PINEAPPLEING SLOW, and this message pops up everytime I turn it on: "Windows cannot find syssetup.exe. Please use the search function..."