unmountable boot failure

i have winxp on a system with a seagate 40gb hdd as master and western digital 10gb hdd as a slave. i recently added a gigabyte vga card and although the os installed it i decided to install from the cd that came with the vga card. it gave an error message for days and finally stopped booting. it would give the message “unmountable_boot_volumn” and to uninstall any new hardware. i removed the vga card but could not uninstall the drivers even in safe mode because it still did not boot. i don’t have the os cd to repair the os installation and did not make a boot disk or recovery disk. i am lost for how to solve the problem.