Hi Alexei F,
Welcome onboard.
I have seen your post in the PC Advisor forum too.
And you have been advised to use TestDisk.

( but it is not me who advised. )
Well, I shall go in a graded manner on this issue.
1. Connect your external hard disk back into an Windows XP machine and check whether you can access the files. If you can, then copy all the files into another media - say another ext. HDD. (Check all your files are OK and not corrupted. Unfortunately you had run scan/check disc in adverse conditions which could possibly corrupt the files.) If everything went Ok, format your ext.HDD in Windows 7.
2. Boot from a live Linux CD/pendrive and if that could access the files, copy them to another HDD either to your internal drive if it has suficient space or to an external drive.
Peppermint3 - Create Live CD/DVD/USB To Use For Emergency Backup
or
Lucid Puppy way to recover files from a non-bootable computer
whichever you may prefer.
3. Use TestDisk. Follow this guide in using.
» How To Fix: External Disk Drive Suddenly Became RAW
Note: You need not create a PartedMagic CD or pendrive. If your Windows is stable, install TestDisk - Windows version and follow the instructions on using TestDisk only.
You may also refer to the guide here to familiarise yourself with TestDisk.
Regain a lost drive using Test Disk - An Illustrated Guide
Note: Post #23 therein also lets you know how to create a bootable DOS pendrive and run TestDisk with it, if you prefer to take Windows out of the loop.
Let us know how you are progressing.