I installed (or better: I began the installation...

) Linux one month ago and now I love it. So yesterday night I used Partition Magic to hardly reduce Windows space and increase the space for Linux. But... horror, when rebooting GRUB no longer works !!!
I have a GRUB promt and no GUI screen.
I tried reinstalling GRUB from CD, both on MBR and on first boot partition sector, I tried installing LILO, but the result is the same.: the GRUB prompt...
I have a boot floppy for Linux so I can access to my system this way, but this is not a solution, of course...
PLEASE, HELP ME: I don't want to reinstall the whole Linux !!! Let me know how to make my grub work again, PLEASE !!!!
P.S.: Be patient : I know this is an old problem and there is a lot of stuff in the forum about it, but in this moment I'm very panicked and I need someone helping me...
Thanks in advance.