Assuming there isn't actually already a bulb with the same name, you're probably using an older version of Holiday Lights, and you downloaded the new bulb directly into your "Holiday Lights Bulbs" folder instead of onto your desktop.

Versions of Holiday Lights prior to 5.0 try to copy the bulb to the Holiday Lights Bulbs folder even though it's already there, resulting in the error message you saw.

The best thing to do is upgrade to the latest version of Holiday Lights from our Download Center. It's a free upgrade for registered users.

If you'd rather not upgrade for some reason, you can fix it like this:

• Open the Holiday Lights Bulbs folder
• Drag the bulb to your desktop (be sure to move it instead of copying it)
• Double-click on the bulb to install it
• Holiday Lights will tell you the bulb has been installed

If you don't upgrade, you can still avoid this problem in the future by downloading bulbs to your desktop, rather than directly into the Holiday Lights Bulbs folder.

 
See also:
How do I know what version I'm using?
How do I upgrade if I'm using a previous version?
When I try to install a bulb, a box appears asking me what program to open it with. Why?