Registry Virtualization is a new technology in Windows Vista that enables registry write operations that have global impact to be redirected to per-user locations. How it can affect the software?
HKEY_LOCAL_MACHINE\Software registry hive was used to store global application settings in Windows 98 time. Later, with new registry security, we moved global application settings out of this hive, and now we store only setup-time settings, which are not modified later. So our software should work fine on Vista with UAC enabled. But if you still using this hive in your applications – be aware that successful write to this hive does not mean other users read stored value. Reminds me “virtualization” of Windows folder in Terminal services environment.