Ive already upgraded my ram to 4gb (its maxed), video card (2gb) and my power supply.  I still want to add a usb 3.0 internal hub in the front, and I was thinking of upgrading the processor to the fastest intel I can buy.  I know they are old but I figure I can find one on Ebay.  I've upgraded AMD's before but not intels, and I'm very confused about all the different processors.   The current chip is an Pentium E2200.   Any help would be great, thanks in advance!

Here is what I have:

I'm using windows 10 home 64bit.  My computer is an old HP.  a6600f.   
Socket type: 775
my motherboard is a:
Manufacturer: Foxconn
Form factor: microATX - 9.6 inches (24.4 cm) x 8.5 inches (21.5 cm)
Chipset: GeForce 7100/nForce 630i
Memory sockets: 2 x DDR2
Front side bus speeds: 800/1066/1333 MHz
Processor socket: 775
Expansion Slots:

    1 PCI Express x16 SLOT for graphics card
    2 PCI Express x1 slots
    1 PCI slot

 
supports the following processor upgrades

    Intel Core 2 Duo (Wolfsdale) E8xxx
    Core 2 Duo E6xxx (Conroe) up to E6850
    Pentium E2xxx series (Conroe) with Dual Core technology up to E2160
    Core 2 Duo E4xxx (Conroe)
    Celeron 4xx series (Conroe) up to Celeron 450

In case I missed something: http://support.hp.com/us-en/document/c01527396
I found Core 2 Quad Q6600 2.4Ghz Quadcores to be the best bang for the buck a while back when upgrading a bunch of dual core SYSTEMS to quadcores. Not all socket 775 boards support the Quadcores, but your chipset says that it should support quadcores. Here are some cheap offerings for the Q6600 and drastic performance gain from the E2200. http://www.ebay.com/sch/i.html?_from=R40&_trksid=p2050601.m570.l1311.R6.TR11.TRC2.A0.H0.Xq6600.TRS0&_nkw=q6600+processor&_sacat=0


*Upgrading Intel CPUs are generally much easier than AMDs because no pins to bend on the CPU and there are notches that match up to socket for PROPER installation. Juts have to be careful not to bend socket pins and not to have anything get into the socket pins, so I always clean the area of the old thermal compound and dust before removing the old cpu and EXPOSING the delicate spring loaded socket pins.I just got the Core 2 Quad Q6600 2.4Ghz today it took about 20 seconds to install, and is working like a CHARM!  THanks for your help!   Q6600's...solid as a rock...Enjoy.