The OS has a built-in driver that should automatically install when the USB cable is connected. Check Windows Update for new and optional updates if you don't see the printer appear. If you use a bi-directional parallel cable (with the computer properly set up), use the Printer Wizard and then the Add Device Wizard (IIRC). The scanner won't work over the network.
Try using one of the programs built into Windows: Windows Fax and Scan (New Scan), Paint (File > Import from Camera or Scanner > New Scan) or Photo Gallery to launch a scan. Alternatively, get a third-party software option (Paperport, for example).
Go here: http://welcome.solutions.brother.com/bsc/public/us/us_ot/en/dlf/download_top.html?reg=us&c=us_ot&lang=en&prod=mfc6800_us
to get a utility to improve the scan resolution.
I hope this helps.
(Scanner problems can often be resolved with a new data cable and a direct connection between the unit and the computer. This assumes that the scanner is unlocked (for those with a transport lock) and that the unit is properly lighting up and the scanner is moving freely.)