here is the 296.10 drivers from nvidia:
btw, thats 64 bit for win7
this is i think the best i got in krombuster, not sure if it passed unigine heaven:
the stock core for the EVGA super clock is 981 core/ 2257 on the memory @ 1.163 volts. right now it is my physX card and its has been a long time since i OC'd it. iirc i never got very far OC'ing the memory, ~ 2300. since you have a 2Gb card you may have a different experience.
i would like to make a few points:
every chip is different; what one card/person does may not hold true for every card so just do not jump on someone else's settings. though the settings may be your "target", ease up to them. you may jump up to a 8% increase on the core and test, but even if that is stable then go slower to just 5Mhz at a time. if you crash goose the voltage just slightly and try it again.
also the 550ti isn't a high end enthusiast card so the memory overclocking with be very limited and won't seem to make much of a difference. i was barely able to squeeze out another 2%.
and keep in mind that some of the more recent drivers do provide somewhat of a performance increase in certain games. so whereas you may not get a overclock over 999 core, the driver itself will give a performance increase so it may not matter. you could consider OCing as far as you can then taking note of your FPS while gaming. then try a new driver and lower your OC. if the FPS is around the same you may just want to stick with the newer driver.
needles to say this all will require a good amount of patience