It's Windows 7 (SP1 x64) with a custom theme.

Edit: Downloading this version fixed it: http://www.neolemmix.com/download.php?program=16

Thanks guys! Now time to enjoy some good ol' Lemmings

I have the same error when it's under "I:\Lemmings" and "I:\NeoLemmix"

It's on my desktop "C:\Users\[username]\Desktop\Lemmings" and running it as admin doesn't fix it, I've also made sure that none of the game's folders or files are set to Read-Only.

Downloaded NeoLemmix and it's quite good, looks nice too. Thanks guys

Although it gives me a save error for some reason

Thanks, that works quite nicely

Hello, does anyone know how to enter proper fullscreen mode or change the game's vertical window width?

It's kind of annoying playing like this :p