it's kinda odd that your place doesn't have a grounding system. I didn't even think that was up to code anymore. What you probably ought to do is get a GFCI plug like this
and then plug it in between the UPS and the power bar. I'm not that familiar with the specifics in the operation of the UPS so it's should probably go "downstream" of the UPS. Since your building isn't grounded, a mismatch between the incoming and outgoing current means either your equipment is getting zapped or you are. This device will detect it and then trip itself off, stopping all current flow and keep you from riding the lightning.
Now these things are designed for a ground lead but it
should still work for you. I'd check with the resident electrician wherever you buy it from.
