After reformatting, did you install the chipset drivers followed by the latest drivers for your network adapter?   All drivers for your system can be found at:

 

http://support.dell.com/support/downloads/driverslist.aspx?c=us&cs=19&l=en&s=dhs&ServiceTag=&SystemID=DIM_PNT_P4_8400&os=WW1&osl=en&catid=&impid=

 

Steve

if your other computer are running okay,,,fast,,but not the one you just did the re-formatt....the chipset drivers,,and then network drivers must be installled...try that,,,and see what happens...sounds like the problem if you just did a re-formatt.. if you still have the problem..you might shut off your computers....reboot the modem,and then the router ,,and then turn your computers on.........

 

also,,you might do this-

 

click on start- control panel- network connections- right click on local area  connections- click on repair...see if that helps...