Overclocking a GeForce FX 5200 safely?

Ok well i did the registry modification to allow overclocking in geforce driver panel and i managed to get it to 291 core/461 memory while testing changes successfully my system specs are and i want to know if it is safe to run these settings or if it's even worth changing the defaults for it:
Dell Dimension 8300
p4 2.6(supposed to be 2.8 but i guess it wasn't the right one)
4x256mb ram
GeForce FX 5200 128mb
windows xp sp2
2x120gb hard drives

i got a 3dmark 2001se rating of 5573 is that decent for this card or is there some way to get more out of the card?

 

You should play a game that is intensive for two hours and check the temps(still looking for one that has history of the temps) and see if the game runs fine(no graphics problem)

 

Overclocking is kind of a guess thing. You have to keep trying, raising the MHz little by little and sometimes lowing MHz little by little, although you have to make sure the RAM or the GPU is getting too hot. My old 5200's core made it to 526 core and low 300 memory.