Wireless connection for beginners

Hi there, I'm hoping to pick up some sage advice from you folks out there. I lack very basic knowledge about computers and this problem is driving me up the wall! Thanks to anyone who is patient enough to answer the querie:
I have just bought an Acer 9301 notebook and cannot connect to wireless internet although the computer recognises the signal from my router. Whenever I try to connect, it says immediately that it is impossible and that I should contact my system administrator. Friends have told me to try and sort out the router/notebook configuration (WEP?) but the two systems seem to coincide. I have also tried every other troublshooting option on the help page but, to tell you the truth, I don't really understand what the final objectives are. What do you think could be wrong with my set up? Is there anything obvious I am missing?
Meanwhile, I have connected the router to an ethernet cable and i'm getting a perfect connection...

Thank you very much for your help, Xochitl

Several things could be wrong: wrong WEP key; weak signal; radio interference; any number of settings causing incompatibility between the router and wireless device, including but not limited to encryption, protocols & firewalls.

You'll just have to tackle it methodically. There is no magic universal solution to all connection problems.