First, the hard drive may be failing. In that case, you will need to use some sort of recovery software or, in the worst case, professional recovery services (thousands of dollars). If the drive is failing, do not do anything that might cause a write to it.
If the drive is fine and the only problem is access, and the directories are still there, as Administrator you can edit the directory protections and make them world accessible. (XP directions, not 7, sorry) Right-click on the directory, select Properties, go to the Security tab, Add an entry for "Users", and make sure that that entry has at least Read and Execute permission. Click on Advanced in the Security tab, select "Replace permission entries on all child objects with entries shown here that apply to child objects," and de-select "Inherit from parent...". Click on OK, and you will grant permissions to all logged-in users on that directory tree.
But this is a write operation, and if the problem turns out to be disk damage, it will make the drive harder to recover. So unless you are _sure_ the drive is OK, try the recovery software.