If u hv windows XP, then its very easy.
1.) First boot using windows XP Setup CD and enter into Recovery Console. Then type following command:
fixmbr
Now reboot ur system, the Linux Boot Loader will be gone
2.) Now boot into windows XP and right-click on My Computer icon and select
Manage, it'l open Computer manager.
Now Goto:
Storage -> Disk Management and remove all linux partitions from there.
Thats it...