Windows 7 Sound + Admin problem

I have this computer since October '09 working with Vista. Right before christmas I updated to W7 Famillial Premium and problems started. First, sometimes after I wake up the comp from hibernation mode, I have no sound. If I restart it, the sound will come back. Also, it looks like it happends when I am leaving a CD in it but I do not know if it's linked or not. Second, I recently bought the two addons for Borderlands (the zombie island and the underdome) and I wasn't able to download the files in the HDD saying that I need admin rights to do so. The thing is: I am the only admin on the comp and simply the only account on the computer. It also does the same thing when i try to extract anything directly on the HDD, BUT, it doesn't ask that if I do it in a folder (for example: program files). I don't really know what to do and I looked on others but it doesn't really help.
Here are the specs:

Windows 7 Famillial premium x64
Model Aspire M7720
Processor Intel I7-920
RAM DDR3 9 Go
HDD 1 To
Graphics GeForce GT 220
Sound Realtek but i don't know the model

So, yeah. Please help me.