how reliable is fixmbr?

[jay cook]

hi;
i have lost/damaged the master boot record on my primary
hard drive. will fixmbr be able to fix the master boot
record without losing any data? it happened with a
program called ez-bios. i was attamepting to install a
western digital hard drive as the 2nd drive. now i have
removed ez-bios but system will not boot. i can boot with
the win-xp (home) cd but an unable to read the c: drive.
i am afraid to use fixmbr command or fixboot command.
thanks.
jay cook