I have tried to install 3 different wireless adaptors.
They all show signals, and show they are working correctly.
The problem is. I can't connect. Tried EVERYTHING.
Anyone have any ideas...

Are you using any kind of encryption (WPA, WPA2, WEP)? If so, make sure you have your encryption key entered correctly.

Are you using MAC authentication? If so, make sure that the MAC address for the computers are added to the list of allowed MAC addresses.

There are many many different things that could cause this. Try the things Spaceman suggested. Also make sure that it is your SSID that is showing up and not one of your neighbors. Make sure there is no interference from cordless phones, microwave ovens, tv's, crt's...etc Many different devices will play havoc with the wireless signal. You may show good strength but not be able to connect.

I dont know if all ISP tech supports offer this service but when I had problems getting mine to connect my ISP tech support helped me. Just a thought. You can also do a reset on the router or your internet tower to make sure they are not blocked, unplug the router do a restart and plug the router back in in 30 secs do the same for the internet tower. And as well as what spaceman said.