Undelete 360 is a powerful free file recovery tool.

It's portable, so there's no need to install anything (which itself might overwrite your lost data). Just download Undelete 360 to a USB drive, point the program at one or more of your system drives, and it'll scour them for the remnants of any accidentally deleted files. This can take a very, very long time (the program isn't quick) but when it's done you'll be presented with a detailed report of everything that's been uncovered.

At first glance this can be such a lengthy list that it's hard to find what you need. Fortunately you're able to filter the files by name, size, creation or modification date, which should quickly reduce the report to a more manageable size.

A Clear "Status" column then shows you the condition of each file, anything from "Overwritten" to "Very Good". "File Preview" and "Hex View" windows allow you to confirm that you've found the files you need, and clicking the Recover button should allow you to undelete them, often even restoring the original file dates and times, and even any associated alternate data streams.