I've got software that don't run on W7...

So, I'm trying to add multiboot W7 and XP on this box. Its already got
W7 installed. I made another disk partition. But W7 Is protecting me
from installing from within the OS. So, I just made a bootable XP
install CD. Same story. XP install disk runs a while then I get a
message from W7 about a virus and it shuts me down.

I guess my next step is to buy a new hard drive, now this is starting
to cost a few bucks. Will it work to install XP to a black hard drive,
then install W7?

Have I missed a better route?

Karl