Microsoft Windows 7 can only show a maximum of 15 icon sets (overlays) per application, and 4 of these spots are automatically taking by the Windows system its self. If you run Tortise SVN or Tortise Git you may have noticed the icons never appear to be displaying correctly. This could be because other programs you have installed like Dropbox, Mozy etc automatically hijack another overlay stop when they’re installed.[/RAW]
Below is where you can find where the overlays in your registry, but change them at your own risk!
Here are the most important icons TortiseSVN uses:
For GIT, right click a folder and go TortiseGIT -> Settings. Then in the left hand menu under Icon Overlays -> Icon Set. This is a full listing of icons used in GIT. Generally speaking you want the main folder’s to take priority, so you know if a folder is up to date or not.
We would love to see Microsoft increase this limit in future revisions or service packs for Windows 7, or for the recently announced Windows 8 (hopefully coming in 2012!)
Source: Stack Overflow