You should be able to upgrade the graphics card without a problem. By using the information supplied by Compaq, I deduced that you could upgrade to any AGP 4x card. The cards listed on the website are the upgrades that Compaq provide. According to specifications the board should have a slot and no integrated graphics, so upgrading should not be a problem.
AGP 2.0 encompasses up to 4x AGP, whereas AGP 3.0 has up to 8x AGP. It should not matter too much about the voltage, as the standard is 1.5v, or the board will have a universal connector that will support 3.3v and 1.5v. As for the AGP 3.0(8x) cards, it is debatable whether the motherboard will support it or not. AGP 3.0 is the first AGP specification that is not fully backwards compatible. There are, however, some exceptions, but that all depends on the board manufacturer. There are some boards that make their AGP 3.0 slot completely backwards compatible and some that are exclusively 3.0. In this case there is not enough information to safely say that you could use an AGP 8x card on this board.
Also, the Compaq seems to support both PC133 SDRAM and PC2100 DDR RAM. The chipset was used as a transition board to test the waters for DDR RAM for Intel. Be wary though as this board will only support two sticks of DDR despite the three slots.
I hope this helped you in making a decision on your future upgrade!
~JncoDragon
