Dual boot

I never have gotten XP to run as a dual boot. I have Vista running OK. I
have XP cloned onto a separate hard drive in its own partition and it shows
up in the boot sequence ( I used VistaBoot Pro) after restart but it always
says it cannot find this file or that one.

If I try to repair or reinstall XP from the original install disk is there a
way to do it that will not erase the data and programs already installed in
XP? In other words a non-clean install.

Any other suggestions?

Thanks,

Paul