PCLinuxOS has a GUI utility for it called redo-mbr. Just pop in a live CD and there you go!But in Ubuntu -1. Pop in the Live CD, boot from it until you reach the desktop.2. Open a terminal window or switch to a tty.3. Type "grub"4. Type "root (hd0,6)", or whatever your harddisk + boot partition numbers are (my /boot is at /dev/sda7, which translates to hd0,6 for grub).5. Type "setup (hd0)", ot whatever your harddisk nr is.6. Quit grub by typing "quit".7. Reboot. OR1. Boot your computer up with Ubunto CD2. Go through all the process until you reech "[!!!] Disk Partition"3. Select Manual Partition4. Mount your appropriate linux partions//bootswap..... 5. DO NOT FORMAT THEM.6. Finish the manual partition7. Say "Yes" when it asks you to save the changes8. It will give you errors saying that "the system couldn't install ....." after that9. Ignore them, keep select "continue" until you get back to the Ubuntu installation menu10. Jump to "Install Grub ...."11. Once it is finished, just restart your computer.