Are your saying that you let Linux take up your whole Hard disk and then you later reformatted and tried to install XP?
If this is the case then your going to have to clear you master boot record and erase the partitions from your hard disk. Doing so is easy and shouldn't take too long.
First pop in a Windows 95/98/ME, if you dont have any one of these then you can download a disk image from the link that I'll post once I find the link

. Next boot from the CD/Disk and choose Start-up with out cd support, not change to the RAM driver it created. Now type in
now just type in fdisk
Choose the option to delete primary partitions and delete all the ones you see, then delete the extended/logic partitions.
Once your done all that choose to create a partition and then once you have your partitions setup install Windows
NOW
If you have Windows XP and you tried to install Linux and you let Linux resize your partitions you may run into trouble. This is a problem that only occures with Windows XP/2K/NT4. Its because XP/2K/NT4 keep track of the size of your partitions and if Windows isn't told of a resize action (from a program like Fdisk or Partition Magic) then it believes your hard drive to be corrupt.
If the second part is your problem then all I can suggest is to try to move you data to a newly created partition.
Hope that helps
