Windows XP Pro Invalid Serial

My friends Acer Travelmate 4400 was completely run over by an 18 ton virus. So I worked and worked and tried everything but nothing could fix it. I couldn't run anti-virus, anti-spyware, or anti-anything programs. I couldn't browse the internet or download files. It wouldn't boot up in safe mode and it was just a wreck. So i brought it home and wiped the hard drive and reinstalled XP pro. Everything went smoothly until it asked for the cd key and when i typed the cd key in that came pasted to the bottom of the acer it says its invalid. What the heck do I do now? i hope we don't have to pay for a new cd key. your help is greatly appreciated

 

Copuld download System Information for Windows from here.

http://www.majorgeeks.com/SIW_System_Info_d4387.html

Once installed,run and go to left and select Licenses under software.
See if it matches what shows on sticker.

 

well seeing how contacting microsoft about xp is now $60 bucks a pop... I think if i have to ill just buy another version of xp. I was wondering if the cd i am using is the retail version and my product key is an oem version would that be the problem?

 

I recall that Adrynalyne mentioned that one could not use an OEM key to activate an installation using a Retail disc and vice versa. See if you can find an OEM disc to use.