Someone listed Baldur's Gate I, Planescape and the Fallout series - all of these are wonderful and I know they will work on a PII because I played them just fine on my old Pentium 200!
I've heard good stuff about the Krondor series, but never played them.
It may still be worth a look, but gettiing the speed of the system to work might be a weird problem (you need a program called mo'slo to slow your system down) - but Ultima VII was a really terrific RPG, the first really nice example of the same sort of top down interface that the Baldur's Gate and later games really perfected. Honestly, it's a been a long while since I've played it, but I remember it as being quite a nice game - certainly the best RPG of its day.
It's not an RPG but it's in the fantasy genre and still a great game, but Myth and Myth II are high on my list of best games of all time - there is now a Myth Worlds (I think that's what it's called) package that has both games and a lot of extra material, further campaigns and such. Now, this is a realtime tactical battle simulator but in a fantasy setting. I mention it because it freakin' rocks - great physics engine, amazing gameplay and some of the best writing, music and voice over narration I've ever seen in a game. Sadly, Myth III which came out about a year ago (by a different company) sucks and was very quickly sellilng for $9.99 - less then Myth Worlds is still selling for!