These would all appear to be PCI cards.
From the
compaq/hp website, it appears that your machine includes a PCI express 16X slot.
Are you confusing these two? "PCI" and "PCI Express" are NOT the same.
PCI is very very old technology, and in fact there is no PCI video card that I would recommend purchasing for windows 7 or at all.
(If that was in fact the only video card supported by the machine, you should get a new machine entirely).
Instead you may want to look at this list:
http://www.tomshardware.com/reviews/best-graphics-card,2387-2.html
The Radeon HD 4650, for example,is a PCI express card that will be more than powerful enough for windows 7. It is similar in price to your listed cards, but is vastly more powerful.
http://www.newegg.com/Product/Product.aspx?Item=N82E16814121338&cm_re=Radeon_HD_4650-_-14-121-338-_-Product