How can I detect if ASP.NET is registered or not (programmatically)?

I've read a lot of posts about checking register, for example:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\ASP.NET\..., but I have not this key at all, and
about existing the folder "C:\Inetpub\wwwroot\aspnet_client"(but it can be absent)

Also I can't use the Metabase.xml because it has different structure for IIS 6.0 and 7.0.

I need errorless variant to detect it.

Thanks, Ekaterina