I bought a used Dell D620 on ebay with a 1.5 ghz Core 2 Duo processor, 80 gb hd, and Windows XP, with 1 gb ram, for about 90 bucks shipped, and also bought the software package with OBD II USB cable from Romania for 40 bucks. Everything was very self explanatory and in a few hours over the course of the day I have INPA, NCS, DIS, SSSProgman, and everything else installed. Works flawlessly.
BMW USB OBD Diagnostic Cable Inpa Ediabas Dis SSS GT1 | eBay
Similar to laptop I bought (the seller I bought from sold all of his)
Dell Latitude D620 14" Laptop Core 2 Duo T5500 1 6GH 1GB RAM 160GB DVDRW WiFi XP 890552699575 | eBay