512 MB is no problem. I've used 512 MB cards in several different Windows CE 2.11 devices without any problems. Theoretically, Windows CE 2.11 can support cards up to 32 GB, but in reality it may not properly read cards bigger than 2 GB. See this tutorial for details:
https://www.hpcfactor.com/support/cesd/h/0012.asp
There've been tons of threads here asking that same question. Search the forums with the keywords "max CF card size" and you'll see prior discussions of this same topic.
