I started using Everything (http://www.voidtools.com/) to help mitigate XP's slow searching and still use it today, even with Win7's much improved search functionality.

Everything Search only indexes file names, so you can't search via date modified or anything like that, but it is super-fast and supports regular expressions. Need to find a word doc that begins with 'ca'? Just type '^ca.*\.docx?', instant results.