I hate to be the bearer of bad news but Its very unlikely that you will be able to recover this data.
However as always things you can try.
Try downloading and installing free(gpl or open source data recovery software) which can recover blocks from your harddisk which have not already been overwritten.
Such as
http://www.gnu.org/software/ddrescue/ddrescue.htmlThis is very time consumining and often can prove fruitless.
One thing to note: If you reinstalled Windows and did not format the drive(part of the install sequence) then your data may still be present in another folder under c:\documents and settings\username
If you are absolutely serious about recovering your data then you should stop using your system right away & take your drive to a data recovery company who will charge you an absolute fortune (usually per MB) to recover any intact data. This is the usually least favoured option and only used in complete emergencies.
I can't think of anymore suggestions than those 3. But I'll keep on thinking ;)