GPS connected to laptop..?

[big.al]

I've read a couple of postings of people that have connected up basic GPS units to laptop PCs, thereby getting a very cheap (and effective) large colour moving map display on the laptop screen (much cheaper than a colour moving map GPS unit).

I have a Garmin GPSIII (not the GPSIII Pilot) which has the moving map, albeit small and grey only.

If I was to get a secondhand laptop to connect the GPS unit to, please can someone recommend;

1) what spec laptop I'd need, if I only use it for this purpose (no point in spending a grand - I'd rather put that towards more flying!)

2) what software I'd need for the laptop to interpret the GPS signal and operate a moving map display.

Any advice from computer-techies or people who have done this themselves would be appreciated!

Thanks