Can you find out when a new user was created in Active Directory on Windows 2003 Server

Have a look at the Account Lockout and Management Tools available on the Microsoft Download Center. Specifically LockoutStatus.exe and EventCombMT.exe. You might not be able to exactly pinpoint where the lockout is coming from but you should be able to narrow it down quite a bit to make it easier to see.

Here are a couple more Technet articles that might help:
Maintaining and Monitoring Account Lockout
Account Lockout Tools (description of the tools in the download linked to above)
Using the checked Netlogon.dll to track account lockouts
Enabling debug logging for the Net Logon service

The quickest way I can think of to show the creation time on a "Scheduled Task" entry would be to execute:

attrib -r -s -h %SystemRoot%\Tasks\Desktop.ini
ren %SystemRoot%\Tasks\Desktop.ini Desktop.ini.foo
explorer %SystemRoot%\Tasks

This would open the %SystemRoot%\Tasks folder in a "normal" Explorer view and would let you review the times on the files stored there.

When you're done, rename and re-apply attributes to "desktop.ini" to make things normal again:

ren %SystemRoot%\Tasks\Desktop.ini.foo Desktop.ini
attrib +r +s +h %SystemRoot%\Tasks\Desktop.ini

It's a cheap trick, but it should show you the creation time on the task file for the task you're interested in.