External HD not recognized/Audio in my DVD player not accessing all from some virus... please help!

So I had a number of viruses on my computer that went under my virus protection's software and i removed them with Spybot and AVG and they appear to be gone, but not without taking a few vital things from my system first. I have a 2004 Dell Dimension 3000 with an upgraded DVD-R drive, an external HD and video card (can't remember the model number off hand) Here are my problems: 1. When I double click on either my C: drive or my H: (external USB HD), i get a "Select the program you'd like to open this files with". So to even open those files, I have to right click and select "explore" and then I can access the files. Do I need a driver for Windows Explorer in order for my computer to recognize the hard drives as a hard drive? 2. My digital camera (Olympus FE-190) has no software it runs as a simple USB drive when connected to my computer. When I connect it, the camera gets an error within its own system. Then, when I disconnect the camera and try and view pictures on it, I get errors on the camera and can't view anything. When I disconnect and reconnect the memory card, everything is fine again. What USB driver would pertain to this type of connection? 3. When I insert a DVD into my D: drive, I get video but no audio. What do I need to install or reinstall? 4. I can't burn audio or data CD all the time, sometimes it works, sometimes it doesn't. Any suggestions? Thank you for any help you can supply!