Hi there
Don't forget of course that you can still use "Classical" VM software like VBOX, VMWARE server / workstation etc even if you don't have VT enabled. You can then install XP as a guest os manually of course.
However in this case you won't be able to run a 64 bit GUEST OS. A 64 bit GUEST OS will require the VT feature (or AMD equivalent).
Incidentally you can actually run a 64 bit GUEST OS on a 32 bit HOST machine (again you must have the VT feature enabled). I did a test of W7 x-64 as a VM on XP PRO.

(Again if you so this the amount of RAM that your VM will use is limited since the XP PRO host will only see around 3.75GB Max).
Cheers
jimbo