NC 8430 experiences and problems

Love the lappy! Oh so very nice. Having some problems though, which some of them I believe are my fault as I tend to not be tech savy (which is an understatement). I began reading the nc8430 thread to see if that could answer my question but after half hour and being only on page 15 with 65 to go, I thought I would take the liberty of starting a new thread!

First, when I installed avg anti virus protection, it scanned the computer and told me it was riddled with trojan horses in what seemed to run of the mill programs such as Ati radeon stuff, windows stuff etc... I only had gone online maybe twice for brief amounts of time before that. Now when I start the comp. I get a error message that windows is missing some Khihihi.dll file. It's not stopping me from using the lappy though.

Second, when I open and close windows, the screen makes a brief weird "electromagnetic like buzz". Not very loud, but certain audible. Is this normal? It don't remember hearing this sound a few days ago?????

Third, can't seem to install the new Ati 7.3 software. Delete the old driver and software and then tried to install the new driver/software. Each time though it tells me it can't do so because the OS or driver are not supported?

Any help on 1, 2 and 3 would be greatly appreciated (I know 3 is a little vague but I don't have my lappy to check exactly what the error is) Thanx.