If you have multiple user accounts on your system, log-in as an Administrator user (in the screenshot, taken from Control Panel / User accounts, we can see our system has two users, "John" is an Administrator and "Robert" is a Standard user; we will then login as John)
Press "Start" button then select "Control Panel"
Click on "User Accounts"
In the next screen, click on "User Accounts" again
Click on "Turn User Account Control on or off"; when Vista asks your permission to continue, click on "Continue" button
Check (enable) "Use Use Account Control (UAC) to help protect your computer" checkbox
Windows will now ask you to restart the computer; click on "Restart Now" button
After Windows has restarted, log in as an Administrator or as a Standard User and install SendBlaster; when Windows asks your permission to do something, always allow the operation. If you are installing as a Standard User, the Administrator password is needed anyway to complete the process.