That lilo 0101 error usually occurs when you're trying to boot your system from either the wrong hard drive (if you've got more than one) or the hard drive where you installd lilo to isn't in the BIOS list of devices to check for a boot file.
To recover lilo, insert the Mandrake install CD 1 and when you get the welcome screen press F1. At the boot prompt type: rescue and follow the screens through to reinstall the bootloader. If you want lilo on the MBR then choose that option. When you're done, make sure you go back into your BIOS and change your boot list to include the primary master drive, which is usually HD0.