Error 1500: Another installation is in progress. You must complete that installation before continuing this one.
Spent most of the time searching on the Internet but couldn't find a working solution. Later, I combined two solutions and it worked.
Here is what I did.
(You should have admin privileges on the system)
Step 1: Open Windows Registry Editor by typing regedit.exe in Start>Run.
Step 2: Go to the location: HKEY_Local_Machine\Software\Microsoft\Windows\Installer\InProgress
Step 3: You'll find that the value (Default) is filled with some data. Double click to open it. Empty the contents for that value.
Step 4: Open Windows Services by typing services.msc in Start>Run
Step 5: Find out the service named Windows Installer from the list of available services. The service would be started and Startup Type will be Manual. Right-click the service, select properties and change Startup Type to Disabled. Click Apply and then OK.
Step 6: Restart computer, after closing all the open windows.
Step 7: Once the system is up after restart, open Services, and change the Windows Installer Startup Type to Manual (You Disabled it in Step 5). Click Apply and then OK.
Now, you'll be able to install any software that failed Error 1500.