First, I ran this thing as my primary computer for YEARS. Everything I'm trying to run used to run fine.
Second, xult is basically Ultima VII.
I used my old p3 for years too.
I guarantee you that firefox will not run well/at all on that machine.
I don't no about other apps, but if firefox is laggy then its not the machine.
Also, Xult != Ultima VII, the under-the-hood changes would more then make it possible to be laggy.
Programs change, stuff moves on. I sometimes have problems with FF on my netbook, and the atom chip is alot faster.
Modern programs use alot more cpu time then older versions of the same program.
My advice.
Any game that can run on your modern computer, use that
Don't install ANY programs other then stuff that won't run on your modern computer.
If firefox or something is installing services or other stuff, then your computer will slow down