Sub weird situation my pc is in

hi, my internet modem dc quite often i mean sometimes its 1 or 2 hours sometimes its not, so we are planning to switch the modem soon, but before that i found out something strange, its like in order for us to reconnect back to internet we have to reset the modem, heres the thing. after reset, my brother's pc will immediately connects back to teh internet, but mine pc wouldnt, i meanmy skype will work i can tlk to my friends on it and such, but i have to wait for like 5 mins or so to resume back to the net on firefox/ other internet dependent program, just not skype though. wonder could any expert here give me any tips , thank you