Slow to open files folders

I have a new computer (1yr) I use at work. Always has up-to-date A/V, spyware, and firewall protection. Ran a scan last night and comes up clean.

Over the past week, I have noticed it takes probably 15-30 seconds to open anything. I had a problem like this before when I right-clicked something, but now it is whenever I open a folder, office file, video, etc. And the computer just hangs until it has finished that process. What can I do?

It doesnt seem to affect internet explorer, but does affect the All Programs list that pops out after hitting the Start button; that too is slow to open