Maybe it could be possible to use a separate indexing engine like this: Lucene.net for the Spotlight replacement
So it could be used also on older machines (I'm an Alfred user at home but I have to use my old Windows XP machine at work....)
I'm not a C# programmer and I cannot even think to start a project like this buti I think that there is nothing similar to Alfred for Windows and it's a void that a well crafted app could fill.