having just recently experienced the same thing I can offer this.........
Did it crash hard, so to speak (ie:did you re-format?)
If not, did you use MS office OUTLOOK for mail (or outlook express)?
If so, look in the following location for OUTLOOK:
C:\Documents and Settings\your user name\Local Settings\Application Data\Microsoft\Outlook\outlook.pst
Or here for Outlook Express:
C:\Documents and Settings\your user name\Local Settings\Application Data\Identities\{E820821D-62D9-4081-965A-4B80A4902837}\Microsoft\Outlook Express\
Change the bits in Bold Red text to match what you have (the last bit E820821D-blah-blah-blah) is a randomly generated string (Mozilla Firefox and Thunderbird do the same.)
Those are the files to look for.