HELP! Recovering lost & Damaged Files & Folders?

I need some tips to software on recovering lost and or corrupted files and folders deleted by check disc during Windows loading. I have several folders and files just missing and some where folders are locked out and say empty, access denied. Can a virus do this or is it just something that happens over time and not being defragged for almost a year? Also need to know how to recover files and folders created as read only from my user acc on an old PC XP install. I dont have the PC ut just the HDD as was and need to recover music and pictures but say I need permission as my old acc was protected and I believe I used the make private function. So now I cant open or copy the files within another XP with my new user acc. I of corse know my old login but no where to inpt it to unlock.

Any feedback is welcomed