If you’re buying a laptop for Z3, and you don’t want to spend a lot of money, there are some desirable features:
Try to get at least 2gb of ram, 4gb is better though it’ll probably double the purchase price and is not really necessary.
Don’t worry as much about a graphics card, if you are looking to save money this would be a good area to not spend so much.
XP 32 bit is probably the most Z3 friendly OS at present (not sure but it seems that way from other posts)
A core 2 duo processor or AMD opteron would be nice, but it’s not nesessary to go overboard here either
Ultimately, your $$ would go much further on a desktop PC.
My laptop - $4000 US
Dell Precision M90
Core 2 duo 2.33ghz
2gb ram 667mhz
nvidia 3500m graphics card
100GB hard drive
17" wuxga screen