computer problems, help needed

i'm sorry for making a new thread asking for help, i'm sure you get this all the time. i know my way around my computer pretty well (atleast i like to think so) but lately i've been having problems, and someone reffered me to your forum because you are some of the most knowledgable people around.

i have been having problems latley and i dont know if its a virus or not. i've had the same hardware setup for a while, then all of a sudden, my computer said it had little or no connectivity, even though mt network worked fine according to my computer. i ended up buying a new hard drive and re-installing windows, everything worked great until i coppied my old music and software to the new drive. now my system runs at high cpu levels, my music skips because of it, windows when it boots up takes a long time to load, sometimes it freezes and i have to manually turn it off and re-boot, and today i booted up, my music worked fine and then within minutes it said i had no audio mixing device...problem is i paid for kaspersky internet security 7 not too long ago and it says that my computer is clean even in safe mode...so does anyone have any advice? do i have a virus? or is my system just getting old? sorry for the speech, i am kind of drunk, but any help would be greatly appreciated.