Installing programs in a dual boot

I'm almost embarrassed to ask this question but will anyway.
In a dual XP/Vista boot, with each OS on a different hard drive, can you install the same programs to the same directory so that even so you have to install it twice (once for each OS) you install to the same Program Files folder?
I've installed Outlook but have both XP and Vista pointing to 1 pst file and that works fine but say I want to install Word, what would be the problem with installing it in say E:\program files\Word etc. when installing from C:\XP drive and D:\Vista drive? Not that space is a problem for me just something I've wondered about.

Hi,

I'm not sure thats gonna work. Some programs installs different settings depending on which OS is on the PC. Obviously the last installation is gonna overwrite the previous one. Tough it's an interesting question...I haven't tried and this is the first time I think on it.
The Outlook is another matter, you are sharing only a database, not a setting or even a program. It will work even if you share it through a network, regardless the OS you have...the only thing you need to take care of is the Office version...

Yeah, my thoughts are the same. It seems sensible on one hand but since Vista is a completely different (whatever) OS, I would think it wouldn't work either. I'm not game enough to try it out even with full image backups. :P