slow boot with XP--not spyware?

Could this be because of a fully loaded registry? you know, when the registry becomes full of useless entries? Has been known to cause such problems.
I'd say give MS RegClean a try (made by Microsoft, no support, available on http://www.download.com) - Simple to use, but not informative and is supposed to solve many issues in the MS Knowledge Base.
Also, maybe your RAM is faulty (which is rare, but causes inexplicable errors - I used to get BSODs) or maybe that your RAM FSB speed (always in MHz - usually 266 to 400).
Maybe getting other hardware componenets tested could help (using software to stress test your hardware is pretty long and leads to indecipherable results), but that may not prove of any use at all. Most windows users experience a slowdown in startup times once Windows starts to get "old".