Here’s Microsoft’s guidance on what operating systems support the 36-bit PAE extensions, and what the memory limits are for each:
http://www.microsoft.com/whdc/system/platform/server/PAE/pae_os.mspx
It hasn’t been updated for Vista yet, but here are the physical memory limits from Thurrott:
Starter: 256 MB (!)
Home: 8 GB
Home Premium: 16 GB
every other edition of Vista will use as much physical memory as the hardware supports.