Windows Vista forum: What the HELL is wrong with my PC wifi

ok I have a macbook pro, which i use as my main computer. then i have a pc that i built, with windows vista. it is my gaming pc. anyway. i can never get this thing to connect to the internet. for some reason the connection is just EXTREMELY slow, sometimes not even working, and other times it just gives me that little blue loading circle and just never connects. i dont even know anymore, it honestly varies all the time, and then for like 2 minutes maybe it will work with a *decent* connection, but it is driving me crazy because i have not really been able to use this computer for a while since the ******* internet wont work. now another wierd thing is that when they are both on the same network (pc and mac), neither one of them one work or both will be extremelt slow, and they are connected to the same network. and i also have ANOTHER router (my family has 2 since one is only B and G and the other is B G and N) one of them it will almost never recongize because it has such a low signal, but on my mac it sees it perfectly and with a good signal and i can use it fine. and other times the pc will see the network and say the pc is connected, but it just WONT LOAD. i tired connecteding the mac and the pc via ethernet cable, so i could share them, connect the pc thru the ethernet and use the mac wifi, but that still wont work... its really starting to get on my nerves, i have no clue what this pc's problem is. Would the problem be in windows vista itself? that is what i am starting to think. should i maybe try and to upgrade the operating system or get a new one? although i will be out alot of money if that doesnt solve the problem. or does anyone else of suggestion or reccommendations on what i can do? its to the point where i really dont/cant use my pc anymore since i want to use it for gaming, but i have to redownload most of my games from steam, plus i like playing online. please someone help me out, thanks