Computer Not Responding

[jaycee401]

I am on windows 7 on my laptop. I used avast anti virus free, but a few days ago everytime I logged on to my works intranet it came up threat detected. The laptop then kept saying not responding and crashing. I got either a blue blank screen or a blue screen with lots of writing but before I can read the writing the computer dies. I have now uninstlled avast and managed to install avg but crashing again. I have to shut the comp down with the off button as it does not do anything when I use control alt delete. Hubby has reinstalled windows but we are still having the same problem. Any advice or help/tips greatly appreciated. Or is it time to call a computer expert to come and have a look?