Help, my windows explorer bugs all the time?

It happens very often but sometimes it just works normal. When I try to open a folder the loading bar goes really slow and the further it goes the slower it is so it actually never reaches the end of the bar. My CPU meter goes 100% and there is nothing I can really do. I close the window but the CPU meter stays at 100%. And now I can't open Windows explorer at all. All other programmerss are running, including Internet explorer (pretty slow though). I end up restarting my computer. So far so good. But now there are three options that may happen. Sometimes it goes normally and starts properly. Other times when it restarts the whole toolbar (the bar with the tasks at the bottom) freezes. And sometimes when I restart it goes to different points of loading and just turns off by itself. May that be some kind of a virus or a corrupted file or something? My memory is only at 51% so this can't be the problem. Please help!