Does the game itself actually lag when you play it? I think the Abe games grab as much CPU as possible, so that they don't lag - they set themselves as a high priority. You could always set it down some, but unless you're trying to do something else at the same time it shouldn't cause harm. It runs at high CPU on mine too, and these are my specs (straight from X-Fire):
Manufacturer:
NVIDIA
Processor:
AMD Athlon(tm) 64 Processor 3000+, MMX, 3DNow, ~2.0GHz
Memory:
1024MB RAM
Hard Drive:
57 MB -I think it made a mistake here
Video Card:
NVIDIA GeForce 7600 GS
Monitor:
Plug and Play Monitor
Sound Card:
SB Live! Audio [9400]
Speakers/Headphones:
Keyboard:
USB Root Hub
Mouse:
USB Root Hub
Mouse Surface:
Operating System:
Windows XP Professional (5.1, Build 2600) Service Pack 2 (2600.xpsp_sp2_rtm.040803-2158)
It isn't a problem with your system - it's just how the game runs itself - I get 100% CPU, and no lag - don't worry about it