PowerShell v.2 comes with a new cmdlet called Get-Hotfix. It retrieves for you all installed hotfixes and updates. You can use it locally or remotely. You should use its -computername parameter to query a remote computer:
Get-Hotfix -computername 10.10.10.10
Internally, Get-Hotfix really is just a WMI call, so this works on PowerShell v.1 as well:
Get-WMIObject Win32_QuickFixEngineering
