Recently, I've noticed that my computer keeps becoming unresponsive.
What happens is that say I insert a USB drive or try to start a game, and the computer becomes almost totally unresponsive.

I am still able to move the mouse (usually) but I cant click on anything.

I have no idea why this is happening, and I havent really made any changes to the system lately (Latest change to the system would have been installing drivers for my new webcam, but that was working fine when I originally installed it)

I have noticed that HDD light doesnt come on like it used to (or at least i dont think it does). For example when Id start a game or something, youd see a constant flicker of the HDD light, but now when I do it, its on for like a second then off for like 5-10.

Any suggestions as to what it might be/how to fix it?
Im borderline about to reformat to see if it makes a change, but because uni has just started, id really rather refrain from doing that.

Thanks

You will have to do some troubleshooting. 

The first thing I would do is monitor your CPU usage for some time (Task Manager).  If the CPU usage is high when you are really not doing anything, the process list can tell you what process it is.  It could be various things, but will most likely end up being some sort of malware.

The second thing I would do is look through the Event Viewer to see if any errors stand out.  Run eventvwr.msc from Start | Run, search box or command prompt.

The third thing I would do is run "chkdsk /r" on all your drives.  Please note that this may require rebooting and may take a long time (hours), so don't do it when you want to use your computer (if it works well enough to be usable).

Thanks for the reply Adeptus. Unfortunately it became to annoying to handle and I just reformatted. So far it is going fine, and I've reinstalled everything I used to have.

I'll keep your solution in mind though if it every happens again (hopefully it wont (YN))