First, let me say that I appreciate that you are creating separate threads for each question, rather than lump them all into one "project". That is much more beneficial to others who may read these posts later.
Psinfo (and the rest of the sysinternals stuff) is really cool. But it is just using WMI to obtain this information. It may be easier to do that as well.
PS > $b = gwmi Win32_Product
PS > $b | gm -memberType property
TypeName: System.Management.ManagementObject#root\cimv2\Win32_Product
Name MemberType Definition
---- ---------- ----------
Caption Property System.String Caption {get;set;}
Description Property System.String Description {get;set;}
IdentifyingNumber Property System.String IdentifyingNumber {get;set;}
InstallDate Property System.String InstallDate {get;set;}
InstallDate2 Property System.String InstallDate2 {get;set;}
InstallLocation Property System.String InstallLocation {get;set;}
InstallState Property System.Int16 InstallState {get;set;}
Name Property System.String Name {get;set;}
PackageCache Property System.String PackageCache {get;set;}
SKUNumber Property System.String SKUNumber {get;set;}
Vendor Property System.String Vendor {get;set;}
Version Property System.String Version {get;set;}
__CLASS Property System.String __CLASS {get;set;}
__DERIVATION Property System.String[] __DERIVATION {get;set;}
__DYNASTY Property System.String __DYNASTY {get;set;}
__GENUS Property System.Int32 __GENUS {get;set;}
__NAMESPACE Property System.String __NAMESPACE {get;set;}
__PATH Property System.String __PATH {get;set;}
__PROPERTY_COUNT Property System.Int32 __PROPERTY_COUNT {get;set;}
__RELPATH Property System.String __RELPATH {get;set;}
__SERVER Property System.String __SERVER {get;set;}
__SUPERCLASS Property System.String __SUPERCLASS {get;set;}
PS > $b | select Caption, Version -first 3 | ft -autosize
Caption Version
------- -------
Mobipocket Creator 4.2 4.2.35
Windows Installer PowerShell Extensions 1.0.0.0
Microsoft Popfly Explorer Beta (1.0.30319.0) 1.0.30319.0