Problem with sql registry

I use "Function CheckMinSQLVersion" from wiki,but result was wrong!Please tell me how to determine is installed(sql server 2005) or not for sure!

If you need only to know if sql2005 is installed you can check HKLM\SOFTWARE\Microsoft\MSSQLServer\MSSQLServer\CurrentVersion\CurrentVersion value.
If it begins with '9' you have mssql2005 installed (sql2000 is version '8', sql2008 is version '10' and so on)
The function in the wiki looks for a specific service pack of sql2000
Hope this helps
Stefano

ReadRegStr $0 HKLM "SOFTWARE\Microsoft\MSSQLServer\MSSQLServer\CurrentVersion" "CurrentVersion"

i try and ReadRegDWORD,and over ten ReadRegStr,sql is installed but the result is ""******??