When it comes to Outlook 2007 Microsoft has done a great job of building in repair features for Outlook. They have a built in memory scanner as well a tool to actually scan for corrupt Office files and make a repair.
Besides having to get used to a completely different layout and having to save files in 2003 format for other people who never use the updates in office the other big draw back is the automatic PST file repair tool that is built into 2007. While it does a decent job at repairing your mail file it still is lacking.
The built in tools is called Scanpst.exe, located at C:Program FilesCommon FilesSystemMSMAPILocaleID folder - normally called1033. Just double click the file and follow the on screen prompts. Be sure to also make a backup of the file when asked. Nothing is worse then overriding your existing outlook mail file.
In about 50% of all cases I have found this tool to work well and fully resolve the issue. You should also note that Outlook 2007 has to be closed for you to run this repair tool.
I know I don't need to say this but I hope you have learned your lesson. It is very important to backup your files in case a computer crash or corrupt files. You should also store them on a separate hard drive to ensure protection.
If the built in tool did not help then all is not lost just yet. PST file repair can be a bit daunting but you can find many other resources online to help you resolve your issues. worst case you can always call in a pro or use a specific software program to help you out
In many cases people loose this file due to a hard drive malfunction. If this is the case then you should expect to pay any were from $159 dollars all the way up to $1800 to recover the information. The lower cost is best case and normally only happens when the NTFS partition is damaged. The higher cost is when the drive does not even spin up and a company needs to take your disc spindals and place them in another hard drive. The best thing you can do is to call around to several computer repair shops and see what advice they can offer. Many places do data recovery however they all do it differently and you need to find an expert at this to ensure no more data loss or damage is done.