It's very simple. What Linux does is replaces some settings in the MBR of the drive. Window doesn't like that tho. What you need to do is clean the MBR Record on the drive.
If you have access to a windows 98 machine then create a boot disk. Of course, if you don't then download this windows 98 boot floppy creator : http://www.bluevolcano.com/stuff/boot95a.exe
Once its done, insert the floppy in the computer, start it up and when the main screen pops up select booting Without the CD-ROM support.
Once you are in the command prompt type :
it will take only few seconds. Once its done take out the disk and press CTRL-ALT-DEL, and go for Windows installtion.
Hope it works for you,