IBM OmniFind should do the trick, It indexes your files and then you can search the index very quickly. It also does caching of documents and other nifty stuff. It is based on Apache Lucene and there is a free (as in beer) version, IBM OmniFind Yahoo Edition. The free version will work with up to 500 000 documents. I used it for searching a number of networked drives with circa 50 000 files on them which it did very well.