Here is the direct way to verify which Exchange 2003 version do you have:
2.Open c:\Exchange Server Setup Progress.log file, which is located on the root of your system drive.
Search for one of the following entries:
[13:47:12] This is a(n) Standard version of Microsoft Exchange Server
or
[14:44:10] This is a(n) Enterprise version of Microsoft Exchange Server
Build numbers and release dates for Exchange Server
How to Determine Exchange Server Edition ,Version and Build number
