I'd second running 64-bit OS's (vs. PAE) in favor of taking advantage
of more memory... But I did notice a common 'gotcha' if trying to run
your "guest" as a 64-bit OS (regardless if your "host" is 32 or 64-
bit): you will have to check your (host) BIOS settings to make sure
your Virtualization / Virtual Machine Monitor (VMM) settings are
enabled to allow the "guest" to run 64-bit. In my case, this was under
Dell:
*
http://www.petri.co.il/virtual_run_a_64_bit_guest_operating_system_in_vmware.htm
*
http://communities.vmware.com/message/1101482
In my case, on two different Dell's, there were either 1 or 3 settings
to "enable" (turn ON) in BIOS (all just related to "virtualization" --
quite straight-forward). I was running 64-bit Ubuntu on the host,
built & installed OpenSolaris x64 gueset, and was surprised that the
"guest" (OpenSolaris) couldn't run 64-bit apps (and "uname" reported
it was not 64-bit). Having already spendt a few hours tweaking the
desktop & installing all sorts of software, I was a bit disappointed
(I already had a 32-bit OpenSolaris VM). HOWEVER: after setting my
BIOS settings on the "host", the guest automatically was 64-bit, too.
No need to re-install... :-)
-m
ps: It's been a couple years since I've tried, but I recall getting an
error when running a VM inside of a VM under VMware (only tried out of
curiosity). But this was under 1.0.something (VMware server).
Regardless, that scenario is probably not going to be terribly
likely / useful? (academic interest)?