I keep the following nifty functions in my Powershell profile, it helps when working with SIDs and Active Directory, it allows you to easily convert a SID back to the NTACCOUNT and vice versa…
function ConvertTo-Sid ($NtAccount) {(new-object system.security.principal.NtAccount($NTaccount)).translate([system.security.principal.securityidentifier])}
function ConvertTo-NtAccount ($sid) {(new-object system.security.principal.securityidentifier($sid)).translate([system.security.principal.ntaccount])}