Relevant links:
http://www.summitinstruments.com/knowledge_center/pdf/TN410.pdf
http://www.lammertbies.nl/comm/info/crc-calculation.html?crc=12345678987...

Adler32 is different from CRC32. It's much faster but a little bit less reliable.
The free ZLIB.DLL from http://www.zlib.net/ has a function to calculate Adler32.