Limited or No Connectivity

I have posted this topic but not in a thread and I am sorry for that. I just new here and I still don't know how until now that I'm posting it thru thread.
I've been connected to the internet using cable connected directly to the port of the wireless modem. But when I tried to use wireless internet connection it didn't work. It is limited or no connectivity. I have Acer laptop with XP operating system. I have tried all the ways to fix the problem but it wasn't fixed. I tried connecting to cable again and its working properly. The tech support told me maybe my laptop has a problem which I don't know.
I have wireless modem beside my laptop. My friend who got inside my room with Dell laptop with XP OS was able to connect wirelessly. I am wondering why I can't connect thru wireless when my laptop and the modem is side by side. My colleagues can connect but thru the use of Alfa Antenna. I don't want to use antenna anymore because the connection is with me only.
By the way, my laptop is just days ago that was changed from Windows 7 to Windows XP. I am thinking maybe the installation of XP is not properly done. What do u think?
Again, thank u in advance for whoever could help my concern.

 

What is the output when using ipconfig /all on the laptop?
Just a thought, but do you have any sort of security enabled on your wireless modem? Is your wireless network the only network that shows up under network connections, or are there others listed? I am assuming that you are attempting to connect to a wireless router, correct?

 

i only have wireless modem not router..I disabled all other wireless network that shows up in the wireless connections..with regards to ipconfig, i think its IP address is 192.168.1.1..i will check later at home the ipconfig /all..i'll email u back the datas that i'll found on the ipconfig..thank you for the assistance..

 

That would be fine, just post the results from ipconfig /all on here. If you are not sure how to access ipconfig do the following:

-Click on start
-Click Run
-Type cmd
-At command prompt type ipconfig /all and press enter

What type of wireless modem is this? If you are indeed receiving an ip address, then I cannot see why you are not able to access the internet. Do you have any other computers on your network?

 

Correct.