I think the MSI PC-MT5 has an nVidea geForce4 MX 420 GPU, i know since I have the board of one in my current rig that the board I got from a PC-MT5 has a geForce4 MX 420SE, same card essentially, you can get drivers from nVidea from here:
http://www.nvidia.co.uk/Download/Scan.aspx?lang=en-ukthis scanner is provided by nVidea, I also recommend you get the geForce experience too as it may hepl you get the best from the card :), before you do install the driver, carefully remove the GPU and read the PCB, the name should be somewhere in the top right near the VRAM on the card, if you cannot see it, the GPU will have info printed on the chip itserlf, carefully remove the clips and take the heatsink off, clear the thermal compound off with a rag and isopropyl rubbing alcogol and take a look, remember to put fresh thermal compound on it, I recommend either ICDiamond, Spire, Biostar, Antec or Arctic Silver, it's easily available from hardware shops and ebay: http://www.ebay.co.uk/sch/i.html?_odkw=ice+diamond&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.Xice+diamond+thermal+compound&_nkw=ice+diamond+thermal+compound&_sacat=0
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