You did something to your boot.ini file that keeps your computer from booting up normally..and keeps bringing your computer in a restart loop?
Ok..usually I would just restore the boot.ini file or edit the boot.ini file from another computer. From another computer you just plug your hard drive as slave...then in computer management you have to mount it so Windows can see it. Then unhide hidden files and system OS file, you'll see the boot.ini file for your hard drive at the begining, just edit it back to default setting. That's why you always make a backup of any system file before you edit it.
Another easier way is rebuilding it, here at this site will give you a guide
Then afterward check that you can boot into XP normal mode..after that if you still can't get into safe mode. I would probably try a repair or check Control Panel/System>Advanced>...something..I forgot.