If you copied one of the "main" folders under your user account such as "My Music", or "Downloads", then yes - these folders are designated as only permissable to the original user. There should be a few easy ways to bypass any permissions issues.
Here's one way that should be solid.
1 ) Right-click the "My Music" folder on your external hard drive, click Properties.
2 ) Find the "Security" tab. Then click on Advanced.
3 ) Then click on the "Owner" tab.
4 ) Click on "Edit" button
5 ) Under the "Change owner to" heading, select your user name (I'm assuming you're an 'administrator' on your own computer), and make sure to check the "replace owner on subcontainers and objects" box.
6 ) Click Apply, then OK. This should effectively give you full privilege of all contents in that folder.
EDIT: I just want to add that Windows Snipping Tool and the new Microsoft Paint are fucking amazing. Incredibly useful, easy to use, and I'll-be-damned
functional. This, alone, would be enough for me to keep using Windows to some extent...