Any additional software will only slow down your pc more
You can perform some cleaning tasks to make it work faster or muy new, fater pc
First of all.
Backup all ure data on an external drive before u will loose it all
Uninstall all unnesesary programs from ure computer.
run msconfing (in start > run) and uncheck all unnessesary software from startup.
unistall your current antivirus and install Free AVG antivirus.
defrad ure hard drive. u can use Diskeeper for this. is very effective and speed up pc a lot.
u can also check ure hdd to look for a bad sectors and u can restre them using Hiren's Boot CD tools.
Update ure windows with the lates updates.