First timer coaxing a Ti4200 into an overclock

Having just completed my first build/overclock (Athlon 2500@3200 on an Abit NF7-S) I eagerly turned my attention to the video card, an Aopen 128MB Ti4200 with the stock cooler, thinking it'd be a piece of cake (asking for trouble!)
First, I can't seem to update the nVidia drivers...the card came with 31.xx and I have 45.xx downloaded (as recommended as the best for this older card). Uninstalled the current drivers from Add/Remove, rebooted and got stuck. Then used a reset programme, removed all nvidia drivers (inc nForce), ran Driver Cleaner to get rid of any traces of the previous drivers, reinstalled the chipset drivers and tried to install the card with the 45.xx drivers but the install programme asked for the cd that came with the card! Viewing the card in device manager or Sandra, the text runs something like "Geforce 4 Ti4200 128MB card with 31.xx drivers" Is this normal?

Anyway, leaving that aside for the moment I fired up Rivatuner. Stock speeds 250Mhz and 500Mhz, but the card is unstable the pc reboots at anything over 254 core and 502 memory! I thought the Ti4200 was a legendary overclocker, am I missing something? Or do you think I just got unlucky?

Any advice on either problem much appreciated. To help out, I have 2x256MB Corsair ValueSelect on loose-ish timings, an Xdream-II HSF and a bit of a crappy generic PSU rated at 350W (I think - could a patchy supply be the problem?)

Cheers in advance

try and install the newer drivers over the original 31.xx drivers

I have attempted this. The driver installation programme seems to complete the task (though it hangs for a long time at the end). I then reboot to find that the previous driver hasn't been replaced. Starting to think a reformat and install the 45.xx to begin with but what a hassle!