Unless there's a hardware problem, yes a fresh install should be relatively zippier than an old one which has become bloated.
You may want to test your RAM for errors and the hard drive for signs of it starting to fail:
RAM test: http://www.memtest86.com/
HDD test: Use your drive maker's diagnostic software for DOS. Links are here:
http://www.tacktech.com/display.cfm?ttid=287
If HDD is Western Digital, CD Image link is here (direct download): http://www.smartestcomputing.us.com/topic/63494-looking-for-western-digital-data-lifeguard-iso/