So, my computer was fine, running as it should and everything, then today I switched it on and windows explorer just keeps closing itself. I'm not getting any error messages or anything, it just...goes!

I've checked the system log and it doesn't seem like there's anything there to me.
I've run hijackthis so can post the log if needed?

Any help would be much appreciated, thanks!

Press Control+Alt+Delete.
Go Over to Processes and then end all processes named iexplorer.exe (if there is any). This might be your problem.

If this doesn't help a fresh restart of your computer is always helpful.
And if worse comes to worse then just try reinstalling your internet explorer.

Hope this helps,
Austin