Re: Is this processor compatible with this motherboard?
There are many Athlon 64 x2, and Athlon x2 chips with HT 2.0 on that particular motherboard's CPU support list. What this means is that even the newer revisions of the older Athlon 64 and Athlon x2 chips will work.
Old chips are not what you should worry about, it's the brand new revisions such as Athlon II x2 240 that might be a problem.
The microcode for your processor (athlon 64 x2 4400+) is **** near identical to the microcode on the athlon 64 x2 5000+, and that chip is on the CPU support list. Technically the 4400 and 5000 are the same chip. The 4400 is just clocked lower. Due to a defect, or perhaps slightly odd behavior at higher speeds. This way AMD saves money because the chip works at lower frequencies, and the chip still works fine. This is also why sometimes low-end models will overclock like champs, and other low end models don't overclock at all.
The point is, your BIOS understands how to work with the CPU microcode in your processor. It WILL work. DDR2 is on that board, and you won't have any problems at all. Newer microcode might be a problem though.