Hi, buying a new graphics card may not solve your problem.
I can't find your motherboard exactly, but the ASUS website shows these similar ones:
http://uk.asus.com/products.aspx?l1=3&l2=149&l3=642
Whether it's
this one or
this one though, they seem to both have VGA ports for the onboard graphics, so you could hook up your monitor to that and try it.
Or is that the problem...do you not have a current extra graphics card, and the on-board VGA isnt working? If so, make sure your monitor a) has a VGA (or D-SUB) input and b) it's set to display from that, rather than DVI.
Failing all that however
this basic ATI 2350 is a ridiculously good purchase for under a tenner and would probably do what you want.