Uninstall MSI from command line

From a command prompt, run with elevated permissions:

msiexec /x {ba5eba11-deaf-beef-ce11-ca5e1337c0de} /qn

where {ba5eba11-deaf-beef-ce11-ca5e1337c0de} is the product code of the application you want to uninstall.

From PowerShell, run with elevated permissions:

msiexec /x "{ba5eba11-deaf-beef-ce11-ca5e1337c0de}" /qn

If you don't know the product code you can get it from the registry, using wmic or from PowerShell using the following command:

gwmi -Class win32_product | ?{$_.Name -match "product name"}

For 7-zip the product code is:

PS C:\Users\Bob> gwmi -Class win32_product | ?{$_.Name -match "7-zip"}

IdentifyingNumber : {23170F69-40C1-2702-0920-000001000000}
Name              : 7-Zip 9.20 (x64 edition)
Vendor            : Igor Pavlov
Version           : 9.20.00.0
Caption           : 7-Zip 9.20 (x64 edition)