I was using bsnl provided nokia modem. i h...

r u using lan connection or usb..need to know..??
assuming that u r using lan connection, u know the primary n secondary dns provided by bsnl (if so), & hv knowledge abt PPPoE connection..if not u gotta clarify more....!!

however, see if ur lan settings are ok n there is no conflict..open Control Panel->Network Connection->right click on Local Area Connection->click Properties->choose Internet Protocol TCP/IP from item menu->click on the Properties submit button therein->manually configure it by clicking on the radio button as 'Use the following IP address'->IP Address:192.168.1.2; Subnet Mask:255.255.255.0; Default Gateway: 192.168.1.1->put the DNS if u hv->nw press OK->OK..
make a through system scan with ur licensed, 'updated' antivirus (i prefer AVG/Kaspersy) and Microsoft Malicious Software removal Tool..
..always better to hv ur System Admin/Vendors supervision....