Hi Mr. Lee,
I think you've got a couple things going on: one we can fix, the other, only a credit card can fix.
First the spikes. There are two ways you can try and fix the audiodg problem, I recommend Pinstripe's fix; it worked wonders for me and many others:
"lag" in online games with Windows 7
Leave the multimedia class scheduler service running, but disable its network throttling "feature":
- Open regedit
- Go to: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile
- There will be an entry for network performance throttling, default value is 10; set it to FFFFFFFF hex (willl look like 0xFFFFFFFF to the right of the entry)
If that doesn't work, then you can try this: Fix: Audiodg.exe High CPU Usage
However, there's going to be a limit to just how "fixed" you can get. Bad Company 2, as I'm sure you're well aware, is a cpu hog. The difference between a dual core and a quad is night and day. Secondly, the 4500 series are budget to mid-range at best. We can't expect great performance out of these cards, so your best bet is to turn down settings. As I understand things, CoH is pretty cpu intense too... I don't have it so I don't know for sure, but I hear it.