I run lap timing software at two racetracks, each track required a pentium 600 or above laptop to power the timing software, we found a seller on ebay who did Dell Latitide machines for about £150 [2 years ago] they were both 1000mhz p3's or thereabouts.
Due to limited finances, and the fact its am amatuer sport, we coudl not run to brand new units.
Anyway, 2 years on, they have both been 100% reliable, both run internet and various other progs and even a coupel of driving games!!, as well as the demanding lap timing software, they are fantastic little laptops that do exactly what you want. I have used them for website devolpment while my main pc was out of service, and we use one of them as a media center for MP3 etc.
The only downside I have found, is that battery life is low - but I dont use them on battery so that isnt really an issue, looking at ebay again, parts and batteries are reasonably priced for these units.
If I had a use for or a need to buy a used laptop, I would go for a Dell again.