3ds Max 7 OS performance question.

Hi everyone, have a Windows 2000 professional machine but something is wrong
with the operating system from what my friend the network guy says and he is
telling me Im going to have to reinstalled the os.  The problem is I dont seem
to have the windows 2000 professional cd and can only get a windows XP disc.  

Im running 3ds Max 7 and would like to know if I would take a big hit in 3ds Max
performance if I get rid of 2000 pro and go to Windows XP.  System currently is
a Dell Dimension 8100 1.4GHZ pentium 4 with 768mb RD ram.  I would buy more ram
but the last time i check the RD ram was a bit pricey, to the point I would
rather just buy a new system (damn RD ram).  Also is there a difference from XP
and XP Professional that I should be aware of, I only have XP.

Any advice on how bad things will get in XP I would very much appreciate it.

Thanks,