E521 overclocking with clockgen advise please

I realise my system is old compared to the vast majority but it has served me well so far and it's not that far off what i need still.
the reason for overclocking is to play skyrim and hopefully mass effect3 (?)

dell e521
vista32 home premium sp2
amd athlon 64 x2 3600+ (1.9ghz)
3gb ddr2 pc2 5300 (2x512@5-5-5-15 3-29-5-3 2x1gb@5-4-4-13 2-20-5-3)
160gb hd
philipsdvd+-rw
nvidia geforce9600gt 512mb ddr3 (replaced 7300le)
19inch 6;4monitor
305w dell psu (264w output)

memory speed is 317mhz and max is 400mhz(x2=634 and 800)

the pc plays dragon age oblivion(morrowindd was better) and mass effect2 just fine. not worried about max resolutions and stuff. just playability. i don't play shootemups, mainly rpgs.

the gpu is just plugged in to the pciex16 slot(had to hacksaw a bit for it to fit) no extra power cable to it.
been running like this fine for a year or two.

overclocking the cpu to 2.2 is fine and runs stable with the fsb at 231 and the ram at 367. i put it through sandra benchtest after playing with the overclock. i can push it to 2390 fsb252 ram399 and seems to run ok until i bench it. blue screen! 2.2 is as high as it will go and stay completely stable. no blue screening.

the mb says 3.0ghz max and 400x2 max for cpu and memory.

am i flogging a dead horse? i've read the current cpu is a very good overclocker but the dell bios and/or mobo is not friendly for ocing.
not that knowledgeable with pcs, but can understand if explained like i'm an idiot.

many thanks