Advice needed for playing live with my laptop

Bit of a vague question.....

Recently been asked to do a couple of gigs, and the last time I played live was with my trusty Jen SX1000 many years ago. Never actually played my "modern" stuff live before, and need bit of advice......

I'm thinking of using my new laptop (Dell Inspiron 1.5ghz, 256MB ram, internal sound), running Ableton Live and a midi keyboard triggering samples etc. Guess I'll need a USB soundcard to avoid latency problems? All of my tracks have been made on either Acid Pro or Cubasis, so Ableton hopefull won't prove too difficult. My music is of the downtempo, chillout variety, and I'm looking to do a fair but of improvisation.

Any suggestions? Anyone gigging with this sort of setup? Please leave comment if you can help!