Posted 04 March 2012 - 08:33 AM
Options now are to try a known good PSU and/or video card, if you cannot borrow a PSU get yours tested by a tech who has the necessary equipment and knowledge, if you cannot borrow an AGP video card try and borrow a standard PCI type (not PCI-E) and try cleaning out the inside of the case from heat trapping dust reseating the add on card securely in the process, see my canned speech below for doing this safely;
If the computer needs cleaning out, first remove the power cord from the wall and open up the case, take anti static precautions before touching anything inside, you can do this by touching a bare metal part of the case, remove the video card, blow out the slot and re-seat the card securely, do the same with the memory stick/s, clean all internal fans, if you use canned compressed air do not let any fan spin freely this can damage them, use something like a clean lollipop stick to hold the fan.
Make sure If all internal connections are secure and that there are no loose components, write down the psu details (make and model) re-assemble the computer, boot up and see how it goes.
Just a cautionary note, if you do use canned compressed air do not upend the can as it is possible for fluid to be emitted.