"Dependency service or group failed to start" and unable to start Diagnostic Policy Service manually

[racingracing]

My access to internet failed since yesterday. I checked and all hardware are working properly. I've done researches and so far, and still no luck, here's what I have done so far after the problem exist:

1) tried to use scannow on cmd, no error found
2) installed SP1 on my Vista as some people said it may correct the problem but it does not, and it also erased all my previous restore point that I could use and may have fixed the problem? :(
3) replaced nlasvc.dll per some suggestion I found online, it's not working either
4) When I opened IE and obviously it'll say connection problem. So I clicked "Diagnose Connection Problems", it says "Network Diagnostics cannot run because Diagnostics Policy Service is not running". So I opened the Service Manager and tried to start the Diagnostics Policy Service manually, it failed with mssg: "Error 5: Access is denied".
5) Some peopel say it is the corruption in the TCP/IP Stack, so I tried command Prompt type : netsh winsock reset and reset, not working.

Any suggestion is highly appreciated. I really hope to fix this without having reinstall the OS :(

Thanks!

P.S. Just remembered something.... the only incident in before and after the problem is, the power failure in my house area, while my computer was plugged in and running without a battery inserted. I'm not sure if that accident shut down is the cause of this problem or not. :(