There are two types of PowerShell versions out there. PowerShell v1 that dates back to 2006 and the PowerShell v2 that is bundled with Windows 7 and Windows Server 2008 R2, and also mysteriously released for down level clients such as Windows Vista and XP (under vaguely named Windows Management Framework (Windows PowerShell 2.0, WinRM 2.0, and BITS 4.0).
An easy of distinguishing both versions is to look for a PowerShell variable called $psversiontable. If it is not defined, then you are running v1. If it is there, you have v2. You can also look at a registry key to differentiate between v1 and v2: HKEY_LOCAL_MACHINESOFTWAREMicrosoftPowerShell1PowerShellEnginePowerShellVersion.
Note that if PowerShell was installed as an update package you may not find it under installed software. You may have to look at the update packages. Also note that PowerShell v2 can be installed over v1 without having to uninstall v1 first. If you were running any CTP versions than the install may make you find and manually uninstall v1 first.