|I can't find that "exact" model; but my impression is that it's quite elderly by current designs and specs.|
For any given system the easiest and cheapest way to speed up a system is to install more RAM. Also to disable//uninstall anything that runs in the background and which you don't need.
Upgrading the processor is usually expensive; and seldom makes that much difference in general terms/use.
Installing an SSD (solid state drive) in place of the conventional mechanical drive will make a difference; but I would be wary of going that route; as the gains may be less than you hope for.
The operating system may also impinge (have an effect) on the performance of a given system The older the kit, likely the slower it will run with a new more current OS.
How olde is this kit, this computer? As it's running Vista it's pretty elderly... so I wouldn't waste my money on trying to soup it up/upgrade it. It possibly will run Win-7; possibly win-8x - but no way anything after that? As you progress from Vista to later OS it's age and specifications become a serious factor.