[changintimes]

a Compaq computer with a Celeron 2.9 GHz processor

or

a Compaq computer with a Sempron 2.0 GHz processor

which would be a better buy?

[Tapeuup]

the cheapest

[loserOlimbs]

The Sempron. The 2.0Ghz Sempron is the 3300+, so it performs as a 3.3Ghz Celeron would, plus it is a socket 754 meaning in the future you could always upgrade to lower end AMD64, and that is a good chip.
Beside that Sempron 3300+ is about the same as buying a Amd Athlon XP 3000 or a 3Ghz P4.

[changintimes]

thank you tech dude loserOlimbs,

i made a mistake in my original post, the computers are both eMachines and not Compaqs,

[CarlssonMB]

I'd reccomend against getting an eMachines