Internet program glitch

my internet used to be perfectly fine. that is until about a month ago, when i couldnt use utorrent anymore. I thought it was just a software glitch, and forgot about it, but then, i downloaded Steam, and it couldnt even connect to the server,let alone create an account. More software glitches, i figured. all my old programs connected just fine. but then, when i updated skype, it stopped working too. as did an MMORPG i kept on my usb. so, i checked out a few forums, and they generally told me to check my pc with Avast and Spybot S&D. so i did. well, partially. Avast came up clean, but Spybot couldnt even download it's database. basically, none of the programs i download can connect to the internet. I cant even update my antivirus, or download from Brothersoft (which use downloaders to download the software). Anyone know how to fix this? I am running a Compaq with windows Vista installed. if anyone can fix this, thx.