CCleaner is definitely good to have and can eliminate a lot of old junk. Also XP-lite might help on removing the unnecessary trash as long as you don't overuse it. Also CachemanXP is worth to install.
One thing worth to check is if the computer is clean from the dust and all fans are working.. Some Intel machines keep on working a lowered CPU speed if they overheat.. Some people have not remembered to clean their systems resulting slowdown on systems trying to cope..
Another, as mentioned is to check what stuff gets started a bootup.. Plenty of programs install themselves waiting, having those pesky icons at the bar ans wasting boot time and system memory.. It should not be so much problem on your system as it has considerable amount of Ram but it might help.
