Most windows 7 compatible computers that have intel chipsets with virtual extensions on the CPU (core i3, i7 for example) and intel graphics chipsets are perfect for programming. In addition look at the kind of wireless chipset that the computer has. Many wireless chipsets have open source drivers available and are automatically configured when you install, but some computers require extra configuration to get the wireless up and running. That can be a pain, particularly if you don't have an ethernet cable. Its the hard way to get started.

Also, you will probably want an HP printer or a printer that accepts Postscript. There are drivers for HP printers on Linux, but that is not true of all Canon, Lexmark, Kodak, Brother etc et.

Also watch out for laptops that feel hot to the touch. Touch the bottom and the keyboard and all over the laptop. The only thing hot should be the air coming out of it. Its a mistake to buy one that feels hot, because that heat is going to slow your system down when you start trying to compile.

Try to get a laptop that is also bulkier. This flies in the face of laptop etiquette, but bulkier means you can get better ventilation as often laptops will have rear exhaust ports rather than directly under the bottom.

If you can't get one of these get a USB powered dual-fan chill mat. They work WONDERS!