For those who can help:

I am getting a new laptop that is sending me a backup of Windows XP on disc. Can I use that disc to reinstall Windows on the desktop that I am selling since I no longer have the Windows disc that came with that desktop? Is this against the law? Will it even work? Please help me out. Also, is it very difficult to actually reinstall windows?

you can definitely use your new win xp disc to install on the desktop.
is there a sticker (usually on the back) of your desktop with a windows xp key? if it does, then just install your new copy of windows with the key on the back of your desktop. (any key will work with any copy of win xp) if the desktop came with a copy of windows, then you have a right to reinstall it on that computer. if you can't find the key, give microsoft a call and they'll give you a new one.

awesome. I was worried that this would be a problem. Will I face any problems reinstalling it if the XP I am getting is a different year than the XP currently on the desktop?

you shouldn't have a problem. are you trying to keep all the stuff thats on your desktop's hard drive, or just wipe the computer clean?

I am just trying to wipe the whole thing clean so that when I sell it it is as close to brand new as possible.

Druucifer, IMO, is way too sanguine about your chances of pulling this off.

Microsoft is not going to just deal you a new license for your desktop if you have no proof that you own a license for it. If you find a CD key on the back of your PC like druu says, then you're probably in good shape, but even that key won't work with the CD you've got. Also, if your old computer had another version of Windows apart from XP on it, you can't just install XP for free.

My guess is that if you want this desktop to be kosher, you or the buyer will have to shell out for a new copy of Windows.

The system is XP sp2 or something. That's the same one that the backup cd is. If I own the computer and it has windows on it, then how would I go about proving that I have XP on my computer to Microsoft? How much does a new Windows OS cost? Is there any way to wipe it clean--programs, cookies, all the different things that have been customized on there by me--without reinstalling? I forgot what people said about this before. Can I format the C drive or something?

Who did you buy the computer from? They might be a better bet than MS to get a replacement CD.

If you format C:, you get rid of Windows, and it's pretty much impossible to clean up your HD/Windows without formatting.

I thought XP phones-home to Microsoft when it's installed, who then authenticates the install after an inventory of your primary hardware is made (motherboard and CPU, I believe) which prevents you from installing that copy of Windows on another machine. I think the CD key is specific to each disc now, unlike previous versions, unless you happen to have one of those corporate mass-install versions.

Ok. I bought my computer from Best Buy in San Jose CA but I have no receipt. You think that BB may be able to help me out with this?

Haq, really? i've used different keys with different cds all the time--i just had to wipe and reformat a laptop, and i used a friend's xp disc with the key that came with the laptop. everything worked fine and i didn't have any problem updating (and i'm under the impression that this is perfectly legal, as long as you are using the key that came with your computer). there's xp key generators in the shadier corners of the internets that seem to work with any xp disc.
and i had the same reaction when my friend told me i could get a new key from microsoft, but i've done it personally. it's true you do need a key to begin with, but they're surprisingly cool about giving you a new one (just say for whatever reason your key isn't working and act like you don't know shit about computers)
also, another option if none of this works, would be to get a system restore disc from the computer manufacturer. it might run you fifty bucks, but its easy to use and will bring your computer back to the condition you got it in.

but you still have the option of doing phone authentication in case you don't have the internet. you can get an activation code over the phone and it will run fine. figuring out how to generate these activation codes is one of the primary ways people pirate software

These require online authentication after 30 days.

xp corp is the bomb.

another (potentially valid) excuse to offer microsoft on the phone when asking for a new auth key is "my motherboard ate it, and I had to replace it." I have done that.

damn, how things change. the last time i had to use one of these was when i fucked up my parent's computer in middle school.

I just installed one a week ago. Then I finally found my corp disc.

so the consensus is: I can try but it's not really 100% that it will work. For the sake of my sanity I am going to go with Uber-nerd Druucifer.

I am going to try it. Worse comes to worst, I will have to purchase the xp system which I may have to do anyway.

If you have to buy, buy an OEM version of XP Home from Newegg.com - it's like $90.

what does OEM stand for?

original equipment manufacturer.

software intended to be bundled with computers/other hardware that the manufacturer had too many copies of and sold on the "grey market."

and while your re-installing windows, you can play pinball, minesweeper, etc. heres how. btw, haq, i posted a question in the bb features suggestions forum.