Part of the Windows installation process is formatting the hard drive, so I seriously doubt its got any connection to the prior installation of Windows. Right click the My Computer icon (either on your desktop or in your start menu, depending on where you put it) and click Properties. Click the Hardware Tab, then click the Device Manager button. Verify that all hardware is installed properly (i.e. no yellow exclamation or question marks). If all is well, open a browser and attempt to access your router or modem. To do this, you typically type something like 192.168.2.1 into your address bar. It varies, so you'll have to read the manual for your hardware. If you can access the router, cross that off as the problem. If your ISP requires any software to be installed, verify that it is.