The answer, I'm surprised no-one has answered, is NO!! You can't!! Compaq don't facilitate it..
It's really a stupid thing to do anyway.. You'd probably only fry something on the board..
If you wish to overclock, buy a MB / Processor combo that was designed for overclocking.. Get plenty of info before even entering the bios as one wrong move could melt the cpu into it's socket..
RAM has to be of excellent quality, as does the graphics card as you're increasing the voltages sent to these also..
Many hard disks will corrupt when overclocked..
Again, it's a stupid thing to do to a computer.. I wouldn't advise it unless you've got money to burn..