The program must have administrator rights...not the computer user who almost always has administrator rights unless you have set up a special user account without administrator privileges.
2 ways to do it with Vista and Windows 7 computers.
Either install the program under the "run as administrator" command line option to start with
or open the program using the "run as administrator" command line option.
When installed under this command line Windows recognizes that you gave the program administrator privileges right from the beginning and you don't have give it the special privileges each time you want to update.
For already installed SleepyHead...go to your Start Menu or Icon and right click your mouse on the program instead of left click to open...with right click of mouse you should get a little box with command options what to do..open...opens it regularly and "run as administrator" choose this one and then SleepyHead will open and have grown up administrator privileges and Windows will allow the updates to occur.
If this is too annoying....uninstall SleepyHead and then re-install with the right click mouse thing instead of left clicking to start the install. Uninstall doesn't do anything bad to any old data already stored. That data is in a separate SleepyApp folder in MyDocuments and uninstalling doesn't remove that file. I know because I did it when my Windows 7 computer gave me the same update problem. I had data from 4 different machines in my user file and I didn't have to re-import anything.
For XP users having the update failure...I don't know what to offer. Sorry. I don't think XP users have the "run as administrator" option line. It has been so long since I have used XP that I don't remember how I used to bypass this problem.