You could do the following:
Get Kubuntu CD
http://www.kubuntu.org/getkubuntuStart the system at Kubuntu Intsalation display, press the F6 button.
At he end of the command line add-- noapic
Then installed with minimal requirements
Let your exisitng partitions in place and create another one
After install at GRUB display you should see something like:
- Kubuntu
- Kubuntu Recovery Mode
- Windos XP
- Vista Recovery
Select Vista Recovery , then at Recovery mode, select the recovery option that
formats the system as it was before your problems.
Hope it works.