How do I fixed grainy images that I scan?

How do I fixed grainy images that I scan? I just got an hp office jet 5510 from my family's house that they were not using. Every time I scan my images look terrible even if I increase the DPI. I can't find any special options anywhere for the scanner, and I cannot find any special software to download for this scanner/printer/fax. I am using Windows 7 64 bit operating system.