Run a good spyware program, (like Spybot Search And Destroy...it is free to download and use) run disk cleanup, defrag your hard drive, and go to Add/Remove programs and uninstall any old useless programs you have loaded over the years and never use anymore.
Check for updated drivers for your system like the video card, network, drive controllers, at the manufactures web site you bought the laptop from, (Dell) DO NOT USE SECOND PARTY OR ANY DRIVERS YOU FIND ANY WHERE ELSE.
That will just about take care of everything they are going to charge you to do.
And it goes without saying, make sure you are running a good antivirus program.
I am sure someone will chime in with a couple other programs or tricks as well.
There are registry cleaners, but I have found that most usually, unless you are extremely familiar with working inside your registry, registry cleaners can do way more harm than good. I suggest staying away from them.