Where are many keyword tools that can e.g. suggest and explode keywords for you, e.g.
A1 Keyword Research. Great to quickly build many keywords, e.g. using 3 small tumblers:
windows xp
windows vista
keyword
phrase
software
tool
=
windows xp keyword software
windows xp keyword tool
windows xp phrase software
windows xp phrase tool
windows vista keyword software
windows vista keyword tool
windows vista phrase software
windows vista phrase tool
You can then permuate, cover typos etc. in above.