trouble with my PC to connect net with BSNL Broadband Modem- reg

hi experts here,

let me discribe my problem,

that, i m using BSNL braodband, in my office. but now, cant connect net with this. One BSNL Man came and checked my PC. he says that, this is the problem of my PC. but i was not there at that time. and afterwrd, have checked. cant found any error with even usb port.

i am thinking that, this will be the problem of any settings.
also to say u that, i m using Win Xp.

can anyone guide me pls

thanking you in advance

wt lov

mobileman