Can I have 64bit Linux installed on my Desktop PC?

Absolutely. This has been the default for a while, and the majority of linux PCs is 64bit already.

All it requires is a reasonably new PC (purchased summer 2004 or later). Where reasonably new means your PC is at least a Dell Precision 370 ("satyr", first purchased in Summer 2004) or a later model (Precision 380 "satyr", Precision 390 "oreade", Precision T3400 "pepe", Precision 3500 "Nomos", ...).

Actually, it's a valid reason to have your PC replaced by a contemporary model if it cannot run 64bit operating systems.

The 32bit variant of SL5 is still available on request, for systems with 3 GB of RAM or less only. The 32bit setup receives little testing these days.

As of SL6, we only support 64bit systems.