One Piece:
Hello and welcome to the forums.
If these are the typical folders saved to your desktop with the old user account name, then you may need to take ownership of them before you are able to delete them. And even after taking ownership you may still need to grant your self full permissions from the security tab within the properties of each individual folder before you can finally delete them successfully.
Here's a link to a small app that might help by adding the Take Ownership utility to the Windows 7 Right Click Context menu. I have often found it a handy tool in these circumstances.
Link Removed
Keep us posted.
Randy