I am currently playing Black Plague, and I'm getting severe lags(around 4 FPS) when around monsters and sometimes random. In normal gameplay I'm getting about 30 FPS which is normal for my hardware:
- Make sure you have the latest drivers for the card.
- Try turning of post effects, shadows, etc and see if that helps.
- Make sure no other program is running in the background taking up power.
- Lower the resolution.
- Make sure the card is not too dusty (sometimes removing dust from fan can help)
On vacation to Florida a while back I only had my mom's laptop to play games on, and it had similar specs and ran slowly. The HPL engine doesn't seem to be very optimized for slightly old cards, but does run very well on newer cards. You may need just more RAM. Barely any gamers still have such small computers.
Seems like a cpu issue then since enemies do take up a bit of cpu.
You should have a powerful enough cpu though and I am not sure what could be wrong. The only thing I can think of (and that I have already suggested) is that some other app is taking up alot of your cpu. Make sure to turn off msn, skype, etc. Anti virus programs or stuff like that might also be the problem.