I had some long start up times that I ended up tracing to Norton. Dumped that for ESET, and boot time plummeted. Another thing that helped was switching from the installed defragger to an aftermarket one - I use PerfectDisc, but there's other utilities as well. What you're looking for is the option to defrag system files on start up. Do that.
Computer => Properties => Advanced tools At the top of the page, you may see a message regarding performance issues.
Check boot time: http://www.vistax64.com/tutorials/151819-boot-up-time.html
Tips to improve boot time: http://www.vistax64.com/tutorials/70563-boot-up.html
General performance tips:http://www.vistax64.com/tutorials/81176-speed-up-performance-vista.html
checking start up programs:http://www.vistax64.com/tutorials/79612-startup-programs-enable-disable.html