I was cheap and bought HP with E-5300 Intel chip.Now ,becouse I want to do High definition video additing i think i need to apgrade to faster chip.How high can i go whith this on original motherboard and power supply?Can i install new I7 quad core chip ?Any  compatability issues will be?I need 3,0GHz or better,do I need Quad core or Dual core is enough?Budget and which MBoard this actually is would DETERMINE that...
iNtel socket 775 chips go from $350.00 down...depending on if the board supports them.How and were can i get this information.If i find out what matherboard i have how to find if that spicific chip will be compatable with it?Your current CPU is a socket 775...
Newegg for example shows 24 of them...
See Here...

You would still have to check the MBoard specs...What if to replace motherboard to new H55HC motherboard with i5 -661 chip.would that work?Would i need to replace something else with that exchange?Sure that would work...you could re-use all existing components.
Only ONE that comes to mind may be your power supply...how many watts is it rated at ?I don`t know.This is relatively new computor,about 6 month old.I will definetly LOOK a little later tonight.Thanks.You came up with the ideas...i'm just answering inqueries...My power supply is 300w,but i m going to install blu ray drive to burn blu ray dvd.Do you think new chip will INCREASE power consumption?may be not significant?What happens  if power supply will be over loaded?Will it burn?Or slow working?You'd be better off just buying a whole new computer. The cost of a new motherboard and cpu and psu and optical drive would probably be as much if not more than a new computer. Plus you have the added comfort of knowing that all of the parts are compatible and work properly. But, if you would like to build your own then we can help you out with that too.thanks a lot.A new machine with a 300W PSU ? ?

What's the model # of this PC ? ?My Shuttle has a 300w psu, but then it is a mini-pc

It`s Hp 6250 I think ,if i remember correctly.But it is 300W LiteOn.Isit too small?how much power consumption of Blu ray burner?I could not find that.Well,450W PSU is not expensive(20-40 bucks).If you are planning on running a Quad Core chip and a Bluray burner you should get at least 500w as it will give you some extra headroom. Also avoid cheap brand ones as they are not as RELIABLE or efficient.

List of good and bad PSU brands: http://www.10stripe.com/featured/psu/brand.php