Windows

If you performed a Format you deleted your Data or at least deleted it from the Master Boot Record. Provided you didn't do anything more here you may be able to recover your Data but it is quite likely you will not be able to recover it to so this is a lot of a Gamble.

What you need to do here is remove the HDD from this Computer fit it to another and run some Forensic Recovery Programs like X Ways Forensics from X Ways but as this is a Forensic Recovery program you need to know exactly what it is you are doing. If you do not know Forensics Inside out you need to send this drive to a Forensic Data Recovery House to recover your Data and even then there are no Guarantees.

http://www.x-ways.net/forensics/index-m.html

This is both expensive and Time Consuming so if it would only be Nice as appose to Necessary to recover the Data just reinstall the OS from the Recovery Disc and work without any of your previous Data.

If you need to recover the Data you need to Stop Using this HDD Immediately and not use it again till the Data or what is possible to recover is recovered. The more you use it now the less likely you are to be able to recover any of the data.

Col

Acctually you could use data recovery software to recover your files even you re-install the OS.
You could use free data recovery software, Google "free data recovery software", there will be a list of information, here is two examples:
http://free-backup.info/data-recovery-software.htm
http://www.softperfect.com/products/filerecovery/

If you don't believe freeware, you could get charged software trail full edition for free from Trailpay, here is one :
http://www.trialpay.com/checkout/?c=2e8cd2d&tid=A7DWWlW