>When using SYS(2007), we can obtain a CRC of an image file. The class I have built in .NET uses the polynomial approach which is what PkZip uses. When running both, I obtain the same number. Does this mean VFP also uses that same algorythm?

I believe so. According to http://www.geocities.com/SiliconValley/Pines/8659/crc.htm CRC-32 for string "123456789" should be CBF43926.

? TRANSFORM(VAL(SYS(2007, "123456789",0,1)), "@0")             && CBF43926.