When you install new PowerShell modules via Install-Module, PowerShell remembers the install location. So it is easy to get a list of modules you installed via Install-Module:
PS> Get-InstalledModule Version Name Repository Description ------- ---- ---------- ----------- 2.7.1.9 ISESteroids PSGallery Extension for PowerShell ISE 3.0 and better 2.2.0 PoSHue PSGallery Script and Control your Philips Hue Bridge, Lights, Gro... 0.14.0 platyPS PSGallery Generate PowerShell External Help files from Markdown 2.4 PSOneTools PSGallery commands taken from articles published at https://power... 1.0 QRCodeGenerator PSGallery Automatically creates QR codes as PNG images for person... 1.0 ScriptBlockLoggingAnalyzer PSGallery Functions to manage PowerShell script block logging 1.0 UserProfile PSGallery This module manages user profiles on local and remote c...
Since newer versions are installed side-by-side, it may be worthwhile to search for older versions that are no longer needed:
Get-InstalledModule | Get-InstalledModule -AllVersions
