Turn off system restore for .msi files

I've just spent far too long looking for this, so here's my note to self for future reference.

When installing a .msi file, you might have noticed your system freezes for a short while. This is Windows Installer saving a System Restore point. Generally, this is good and we like it. When you're developing a .msi file, it's more than a little inconvenient.

Fortunately, you can disable it by setting a policy registry key, as documented here at MSDN.

Normal caveats apply - only do this if you know the consequences (no sorcerer's apprentices, please). Unless you're actually installing and uninstalling products literally all day, every day, don't set this.