A Virus?

When I went to start my PC today, it came up with Windows Boot Manager, and I pressed enter to start Vista normally. All was well, but when I opened one folder with some notepad documents, it went crazy and when the window for the folder came up, it flickered through lots of other folders showing their contents, until I closed it. Since then everything has worked normally, I made backups of some important files with uni work etc just in case.

I haven't had any signs it might be infected, it works quickly enough. The only thing I can think of is that quite a few times the web page I've been on has closed down, with a message saying 'Internet Explorer has stopped working'.

So, should I do anything/any recommended programmes etc... :help: