If you have large collection of files and you need to search some files in this collection, then the usual windows search will be very time consuming. This is because for each search, windows searches through the file system. An alternate method is to have the collection of files indexed using a program and search the index. This is very faster than searching through the file system. Only thing is that you have to reindex the index whenever the files in the collection changes.
One such program which is easy to use is Index Your Files. It is very easy to use, portable and supports boolean searches. It allows to keep multiple indexes and search can be restricted within selected indexes.