Which LGA775 socket, non-Extreme Edition CPU?

Best you can use is core 2 duo Conroe E6xxx, they are hard to find now a days but possible used on ebay.

The link you provided says that the motherboard supports up to the most powerful core 2 duo.

You did not provide enough information for me to be able to provide a good recommendation. You failed to provide:
-A pricerange
-the uses of your computer
-place of CPU purchase

Also, for all we know, since you didn't provide your complete system specs, your CPU may not be the component holding back performance.

Anyway, on to my suggestions with the information given, broken down into "best bang for buck". I am going to assume you are using newegg.com to buy from. I am also assuming you have no intention of overclocking or modifying your system from the bios for higher performance.

Least expensive upgrade recommendation: E3300 2.5GHz dual core (actually, if you do want to overclock, I've heard this one overclocks well)
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Under $100 best upgrade option: E6700 3.2GHz dual core. will be a good performer.
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

I don't have any recommendations for the core 2 duo line because the previous processors are core 2 based but with less cache. and the clockspeed increase of the E6700 will make up for the extra cache that any core 2 duo withing $20 could have.

Another option is any dual core Exxx model in between. You can look at the clockspeed for the mostpart between these models to compare.

But really, the least upgrade I recommend is $50 for the E3300. Nothing lower is worth it.

I fail to find that his mobo supports the pentium dual core wolfdale http://www.asus.com/Product.aspx?P_ID=k3h0ZFVu9Lo1dUvk

Is the Wolfdale processor one of those extreme editions?

I see the following on eBay, are they suitable candidates?

Intel Core 2 Duo E6420 CPU SLA4T Conroe
7 Bids $16.50 Time left:1d 3h 33m


Intel Core 2 Duo E6550 CPU SLA9X Conroe
9 Bids $17.49 Time left:1d 3h 36m


Intel Core 2 Duo E6300 CPU SL9TA Conroe
1 Bid $9.99 Time left:3d 3h 39m

E6420 and E6300 are on the supported CPU list not the E6550. If you can find E6600 or 6700 you will be better of because of the higher clock speed.
Wolfdale is a newer version of the core2duo.

His board doesn't support 45nm CPUs as far as I can see.

You're stuck to 65nm ones. Whats you're budget?

The budget is lean, summer quarter student aid barely covered tuition (23 credits). eBay has several E6600's that (so far) are cheap, but I keep getting outbid, dang it! I just use the machine for Office 2010 and photo stuff for reports and the like.

I do not even see where it says that motherboard will support any core 2. That is a pretty old chipset.
Edit* nvm I found them. Firefox was acting weird

In all fairness, even an E2xxx series pentium dual core would be an upgrade over a p4

Best answer selected by stevew_51.