There are answers to several common problems on the Polaroid a520 Troubleshooting guide
Memory: The a520 comes with a 16MB internal memory. This can easily be upgraded with a memory chip from 512 MB up to 4 GB.
Identification and Background
To verify that the camera is an a520, you can look at the white sticker on the battery cover. At the top right in bold it will say a520.
The a520 is both PC and Mac compatible. It has a 16 MB built in storage and is SD compatible for extended memory.