I run a Medion laptop with a Pent. 4 2gig processor, a twenty Gb hard drive, windows xp home and a 32mb ATI Radeon graphics card. 512mb of DDR memory helps a lot!
FS2002 with Wilco publishing's 767 PIC runs perfectly smoothly and I find that if you are not looking for scorching external graphic scenes then this fit will be fine.
For IR work having lots of memory and a sophisticated IR program should be enough, but an 8mb graphics card is whoefully low for today's flight sims.
Whatever you choose make sure you can add memory easily and that your laptop has a separate graphics card, and not the 'shared graphics' that are favoured by Sony and some budget models.
Happy Simming.