Unfortunately, unless you had used the upgrade version of windows 7 to start with and not used the clean install ever, all your programmes, games, whatever ( on "c" ) will be gone and you will need to install them all again ( if they are compatible with windows 7 ), you may have moved the folders of the programmes but there are also registry keys and hidden folders that you would not have been able to export or move to windows 7.
also, now you have overwritten or formatted your hard drive, even if you installed windows xp again.. you will be in the same situation, so the best advice I can give is to carry on to get it all working again.
That is what a 'clean install' is, it removes everything in that hard drive and installs windows onto it