How to execute an action based on registry values?
$rKey="hklm:SOFTWAREWow6432NodeMycompanyMyProjCore"

DBServer="Installed"
 AppServer="Installed"
 WebServer="Installed"

if DBserver="Installed" Then do some action
 Else Do nothing

 If Appserver="Installe" then do some action
 Else Do nothing

 If Webserver ="Installed" then do some action
 Else Do nothing

$p = Get-ItemProperty $key

if($p.DBserver -eq "Installed")
{
   .. do some action ..
}

if($p.Appserver-eq "Installed")
{
   .. do some action ..
}

if($p.Webserver -eq "Installed")
{
   .. do some action ..
}