Hi all.
First of all, I should say that I love this cool technology.  It feels like you're really there.

Here's my problem:
I'm trying to make my own synth, but every time I click on the "make synth" button, it tells me to install Photosynth.  This is even though I've already installed it.  Help?

Mine's doing this a year after your problem. They haven't fixed it yet.

Sue, I see you've created synths just about a year ago so it must have worked for you sometime.

I'll just run through a few facts for you which may help you clear this up.

:1: To *view* synths, you only need Microsoft's Silverlight web browser plugin. This works on modern Macs and Windows PCs. If Novell's Moonlight team can ever catch up to the Silverlight team, then you can also view synth's on Linux.

:2: To *create* synths, you need to install the Photosynth synther program. You can only use this on Windows 2000 and above. Installing the synther will allow you to upload your own synths. 

:3: If your graphics card|video card is modern enough and you have the latest driver files for it and have DirectX updated, then installing the synther also allows you to use the older (but faster) Direct3D viewer, but again, only on Windows.

The takeaway is that the viewer and the uploader|synther are two different programs. You may not have installed both.

To spell it out a little more: 

To view synths you will have downloaded Silverlight's installer from http://www.microsoft.com/getsilverlight/

The exact file: 
Windows: http://download.microsoft.com/download/C/5/8/C5877489-8022-42A6-8456-D05C2A6C8DFB/runtime/Silverlight.exe
Intel Macs: http://download.microsoft.com/download/C/5/8/C5877489-8022-42A6-8456-D05C2A6C8DFB/runtime/Silverlight.dmg
Linux: http://go-mono.com/moonlight/prerelease.aspx (Still building Moonlight 3 - The current Photosynth viewer is a Silverlight 3 app.)

To build and upload synths and get the original Direct3D synth viewer, you will have downloaded the synther's installer from http://photosynth.net/create.aspx

The exact file: 
Windows only: http://mslabs-999.vo.llnwd.net/e1/installer/PhotosynthInstall.exe

Older versions of the synther will automatically check to see if there are any updates and download them before allowing you to sign in or upload any new synths.

Redsux, 
    I am having a similar problem...I go to create a synth and add my photos but the button that allows me to create never actually lights up and I can not do anything. Anyone know how to get past this obsticle?

Hi there, lhetrick, 

What you're probably missing is a title for your synth. Once you have a title in the upper left hand corner and more than three photos, the [Synth] button should light right up.

Wow...well that makes me feel stupid. Thanks Nathanael for the help, that was my problem.

Ha. Don't sweat it. Most people have gotten stuck there before.

I first got stuck there after already creating my first thirteen or so synths. I'm not sure if that's better or worse than you. ;)