Microsoft Windows has stopped working

You should be able to access a restore point in safe mode that will reset your computer to an earlier date. This may work.

Try a restore point, that will be the fastest and easiest fix if it works.
If that fails, try removing startup items (msconfig.exe can do this, and is built into windows) or if you recently installed any programs, uninstalling them to see if they are causing problems.
If that doesn't work, you can try running in a command prompt (Administrator mode if Windows Vista78) "sfc /scannow" (no quotes). That will scan system files and try to fix them.

Oh dear.

Have you tried turning it off and on again?

Copy your entire steam game folder one an external hard drive, format your pc, install steam and put your game where they were. You just have to install them again ( it will discover that the folder already exist and no need to redownload all your game again)

Same happens to me on my other computer :(

This was standard behaviour in Windows ME. In fact, most ME users dreamed of a full 15 seconds of stable operation... I assume you're using a more recent version.

Hope you get to the bottom of things :)

I believe that is not a good sign.

You are lucky to be able to run in safe mode. I suggest backing up the necessary files on your hard drive and then reformat the whole computer.

boot up in safe mode ( F8 ) just after bios screen and select safe mode and run a virus scanner ? and use ccleaner to clean temp and registry strings