Vista virtual machine in XP system

Hi all. Where I work we're almost all using Windows XP SP2. We are now beginning to deploy Windows Vista. We're trying to figure out how to support both OS's at the helpdesk. One idea is to install Vista on our XP machines and dual boot. I had an idea to install Vista in a virtual machine using Virtual PC. We could each then launch Vista as needed. One caveat I see is that Vista is a resource hog and thus the helpdesk machines would need plenty of RAM. Do you think 3 gigs per machine is enough for both XP and Vista? I'd go to 4 gigs but my understanding is that XP can't really use 4 gigs due to a problem with virtual address space limitations inherent in 32-bit systems. Let me know your thoughts.

Yes, 3GB will be enough for WinXP and a Vista VM. A better way might be to install 4GB (or more) of RAM, run Vista x64 as the Host and WinXP as the Virtual Machine.

Thanks for the quick response, SuperSparks. That's not a bad idea at all. However, will the 32-bit apps we run (like Office 2003, Adobe Reader, and other company specific) run without a problem on the 64-bit version of Vista? Also, doesn't Vista 32-bit support 4 gig virtual address spaces, so 4 gig of memory would actually be fully used even in the 32-bit version of Vista?

Pretty well all 32-bit apps are fine on Vista x64 - I've been using it since the early betas with very few problems. The only exceptions are the small handful of apps that have a driver component, but they all have updated versions that run fine on x64 by now.

The 4GB limitation is fundamental to all 32-bit OSs, so Vista x86 suffers from the exact same problem as WinXP.

Do those machines have 64-bit processors?