Help, can't access directories, control panel

Hi, got a new computer about a month ago and immediately installed Avast as anti-virus. Also have been using Peerblock. Haven't visited any sketchy websites or opened any suspicious e-mails/programs as far as I remember.

Last night, I noticed my network icon in the bottom right showed a red "X" even though I am still able to use the internet. I then noticed I would get an error whenever I tried to click the icon to access my directories under explorer or access the control panel. The error message in each instance is "Windows cannot access the specified device path or file. You may not have the appropiate permission to access the item."

I am the only user on the computer so am the Administrator. I have 2 Harddrives, both have Windows 7 64-bit installed, the primary being a solid-state drive, and the other being a conventional HD.

I ran a full Avast check which didn't find much, just 1 sketchy mp3 I've had for a long time on one of my external HDs (I have 2 connected total) which didn't solve the problem. Also downloaded and ran Spybot S&D which found 2 things but correcting those didn't solve problem. I've rebooted several times and nothing has changed in terms of my access.

Also, sometimes when I'm trying to install something it'll say that Windows Installer is messed up and I can't even seem to replace that via the files I tried to download off microsoft's website.

I haven't tried booting from my conventional internal HD but I'm afraid that'll get corrupted too so I'm hesitant to yet.

I'm kinda freaking out. Could anything other a virus cause this?