Try GetDataBack

http://www.runtime.org/

如果系统重装没有覆盖太多文件, you may still have a chance to recover most of the files. It really depends on how you re-installed your OS. I believe the default HP OS restore formats the HD first, then extracts files from a restore partition (typically D drive) and copy them bit by bit to C drive. The format process probably already wiped out whatever you have saved as "backup". You can try GetDataBack to recover that "backup" file first.

I believe BartPE CD also has a program to recover files. I've never used it though.

You might want to take that HDD out first before more damage is done due to tampering.