It probably is not much of issue based on your usage, use your Windows Task Manager to monitor your CPU usage. But for a very small amount of money ($13.50) you could double your CPU's power by getting the E8400 from here
https://pcpartpicker.com/product/Kwbp99/intel-cpu-eu80570pj0806m
If you want to look at faster processors then we need to determine your mobo model, it will determine whether you can use a quad core CPU.
http://en.community.dell.com/support-forums/desktop/f/3514/t/19511448
To determine your system configuration download this program (its free)
http://www.cpuid.com/softwares/cpu-z.html
It will extract information on your CPU (CPU/Caches), mobo (Mainboard), memory timings (Memory), installed RAM model and standard timings (SPD) and video card (Graphics)
http://www.filecluster.com/reviews/wp-content/uploads/2...
As well, open up the case and look at the Power Supply Unit (PSU), there should be a label which gives you make and model. If you want, just take a picture and upload it to the Imgur website, it is free to join.
http://imgur.com/
Once you have this info then provide it along with a budget, country of purchase and any local online vendors you wish to use.