What do you mean you can't access it? Are you getting a "access denied" error or something else? If it's corrupt, it's would be due to the undelete not being able to recover the file properly, there is no way to restore a file once the file system is corrupt for it, without a backup.
If you just get get to it due to permissions, you can take ownership of the file as an admin account and grant rights to any other account after that.
If he can see the file and open it using a clean installation of Outlook or better still, import it into Thunderbird, he doesn't need a converter. If it is corrupt, his malware scanner may be able to help.
You will need to use the the "Inbox Repair Tool" to recover the deleted the pst file of the outlook. First you need to run the tool known as "Inbox Repair Tool" i.e "SCANPST.exe". You can use the "Windows Search utility" to find this file. This tool is used to make the backup of outlook pst file. It is also used to repair the pst file or recover the deleted pst file. I hope this may give help to recover your deleted past file.
You can't recover that user profile but you can access that pst file with the help of a pst recovery software, go for Kernel for PST recovery software for the recovery of your mails etc from that corrupted pst file. It will recovers deleted emails, email attachments, calendars, contacts etc. for more details - PST recovery
There are many third party utilities available that recover the .pst file, but not the user profile. I have used the reliable PST recovery software to recover my outlook data from corrupt .pst file. This software recovered all my outlook data without any loss.
Download Remo Repair Outlook (PST) and check whether your data has been recovered or not.