Windows XP Internet connectivity

One of my PC has original version of Windows XP in French language, after new installation and ADSL modem installation, the moment I connect internet, the receiving and sending data became full and processor became 99% occupied….. 1) Installed more than 4times from format hard disk 2) Checked for warm and spyware nothing was detected 3) Disabled the automatic windows patches updates 4) No other software is installed except drivers…. this is FUJITSU desktop PC 5) PC work perfect before connect Internet but after it becomes crazy… 5) This is original CD along with PC so product key is embadded .. past 2years it is working without single problem but suddenly it crashed and forced to format and re-installation

Any one give me suggestion that how can solve this PC problem ??

Thankx,
Cabir