I had the same problem, and I found this answer on php.net (not my text, not yet tested by me):
IF YOU HAVE A MISSING ODBC32.DLL error come up from your WIN 98/Apache install, you will need to go to Microsoft, right here at http://support.microsoft.com/support/kb/articles/Q140/2/55.ASP EVEN IF YOU DON'T HAVE OFFICE OR WORD, OR ACCESS..and download the ODBC. Go ahead and install. One minor note: the MCsoft instructions say "type command in setup," what you do instead is double click on DISK1 and DISK2 and it will self extract. It will install on your hard drive. Next go ahead and run your PHP script, and Wallah, no MISSING ODBC32.DLL file.
I saw some of these questions, and I wanted to come back and tell others, so you won't have to go through what I went through.
