I just bought a GT 240 for my Dell Inspiron 530. The specs are:
Intel Q6600 (2.4ghz)
350W power supply
Intel GMA3100 onboard video
Vista 32 bit
The problem is, every time I try to install the drivers and restart, I get stuck at a black screen just before I see the login/welcome screen. If I wait for the black screen, it eventually turns into a blue screen error. The card boots up in safe mode, so it can't be the card's problem. I've tried to use Driver Sweeper but that still gave me the same problem.
If you try each stick and find the one that giving you BSOD then that's a bad stick of ram...
I had the same problem, I figured out that my power supply unit (PSU) was 400W(unrated), and to run all installed hardware along with gt240 I needed more power so I upgraded my PSU to 600W. I am now free from blue screen error messages + it never stuck again.
hardware would crash with inadequate power while booting or sometimes during heavy graphics, as the required energy to lift the load is not available.
I think 500W and above would be sufficient, but I wanted to be on the safe side.