a. What is the update you’re trying to install?
b. Were you able to update before upgrading to Windows 7 Professional?
c. Have you activated your copy of Windows 7?
Download the standalone package of the update and try installing the same and check if that fixes the issue.
Method 1:
Microsoft has released a new "Fix it" solution that should automatically solve your problems with Windows Update. Click the link below and follow the instructions.
The Windows Update Agent lets you manage which updates will be installed on your computer. The Windows Update Agent works together with the Windows Update Web site to provide the latest updates to your computer. The Windows Update Agent also works together
with servers that are running Microsoft System Management Server and Windows Server Update Services (WSUS) in a corporate environment.