Once the drivers for the printer/scanner are downloaded from
Here and installed you can scan a couple of different ways.
First is to use the scanner software (ScanSoft™ PaperPort® LE for Brother) on the original cd. If it is not installed already, install the software from the disk. If you do not have an original disk, you can obtain one from Brother for a fee.
Second is to use a different method/software for scanning. Since the scanner is TWAIN compliant, you can use any software that can import from a TWAIN compliant device. Since it is common,.. you can use Microsoft Word or Publisher (Example: from Word XP - from the top menu, click on Insert - Picture - From Scanner or Camera then select your Brother 4800 from the list)
If you dont have Word or cannot obtain it, you can download and use the latest version of openOffice for free at openoffice.org
Here
With either method,.. you will have to make sure the drivers are installed for the printer/scanner.
If you need any further instruction, please comment on this and I will answer your questions