Modified Outlook Account and now I cannot get into Outlook

I am working on my brother-in-law's PC. The PC was configured by the IT department of his former employer...it was using Exchange.
He is currently using Outlook express with an ISP but was using the calendar from Outlook. I wanted to set-up Outlook for him via his ISP so he would not have to use 2 different applications.
I was trying to modify his Outlook e-mail account to remove Exchange and set-up a POP account. I modifed the existing account and then I got an error message, I tried to reverse it but it would not let me and now I can't even open Outlook. I need to recover the file and searched on the internet and only found references to OST to PST conversion. But, there are no free conversion utilities....will that even fix it?
Do I need to reinstall Outlook?
Help Please!!!

 

Using Outlook 2003

 

Is Outlook asking for a new profile?

 

No, I cannot even get into Outlook...

It tries to open, but then it just closes.

 

Taken from another site

often it is a problem with the .pst file (the file containing all your emails, folders, contacts etc.)

Do a windows search for *.pst and it'll come up with the file (not sure where the default location for it is). Copy the file to 2 different locations (preferably at least 1 onto different media, ie. CD-R, usb stick) and delete the original. Now try opening Outlook. It'll ask you to locate your .pst file.
hope this helps

ps- in Outlook 2003 to tell it to use .pst file in a different location click File>Data File Management... and then "add" the newly located file.

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Try command line, start, run
command line 'Outlook.exe /safe' then 'Outlook.exe
/ResetOutlookBar' then ''Outlook.exe /F'

 

Yes, it always prompts me for a username and password...

because it used to connect to an Exchange server. He no longer works for the company. I uninstalled outlook and reinstalled but it still prompts me for the UN and PW. There is no .pst file.
He was just using Outlook for the calendar and he uses Outlook Express for his email.
Now that he cannot get in, the calendar is lost. There is a .ost file but I cannot convert it without having to pay for it......By the way, thanks for all your help!