Problem for creating Registry in vista operating system

Question

Hi,

I have a product whose license key i distribute to those users who purchased the full version,
this key i write in the registry. But some of the users having windows vista are facing problem
that the key is not saved in the registry .

I am using the ModifyRegistry class from the below link:

http://www.codeproject.com/KB/system/modifyregistry.aspx

Regards
Neha