ill do a full tut for you this sunday after noon, all you need is to follow it iam new to exchange2003 but so far everything works. didyou run /forest prep and then /domainprep
1)ok stick exchange cd in drive
2) start-->run--->cmd
3)e: to go to your cd if its e
4) cd setup
5) e:setup>cd i386
6) e:setup\i386>setup /forestprep
then you get a gui and it should say forestprep in drop down window next too microsoft exchange
7) select messaging and microsoft exchange sys tool
next
8)when that finished do for domainprep.
after that run Run ORGPREPCHECK at a command prompt
drive Letter:\support\exdeploy\exdeploy.exe /gc:global catalog server name /t

rgprepcheck
view :\EXDEPLOY LOGS see if both domain and forest prep have installed correctly.
after that just install exchange, one you do that ill finish of the tut.