Moving lap tops, desktops, operating systems or having a developer move on all cause issues with occasional items checked out to workspaces you have no control over.
There is a good blog post here on how to resolve these issues with the command line and TF.exe. You may remove workspaces or undo checkout locks on source code by using the commands outlined below.
Undoing a checkout that belongs to another user
James Manning's blog
The key command for my own reference is:
Had to use this today after finding a couple of instances of code checked out on my old vista installation but the files had been migrated to my new Windows 7 install. So undid the checkout finished the changes and checked in the new versions.