The 512 mg of ram and Windiws Vista won't cut it.
It should have at least 1 gig of ram and preferably 2 gig.
Looking at the 2 you picked the compaq has a bigger hard drive and has 64 meg dedicated graphics so that would be the one just not enough ram.
If you can afford it, spend a couple hundred more and get one with a Intel or AMD duel core processor and at least 1 gig of ram, it is well worth the extra money.
both costs about the same price, it seems that gq desktop is a little bit slower?
Compaq Presario Desktop with Intel