I have had excellent success speeding up machines to their original speed by using System Mechanic.
I does a large number of operations that removes various clutter items, defrags the registry, cleans up memory. It also provides a simple way to review what starts up at boot time and modify as you see fit.
The number of programs (or fonts for that matter) installed on your hard drive has no impact on system performance. The conditions of the registry, whether the drive is fragmented and what programs are started do impact performance.
CCleaner is another program I use often. It is also a big help.
I use these on the 8 computers I support for family and friends and clubs.