Weird E6850 cooling behavior

I'm having some strange cooling behavior in my E6850-based system. Specs are:

Intel E6850, not overclocked
Stock CPU cooler
ASUS P5Q Pro MB
MSI Radeon HD 2400 Pro graphics (lame, I know, but it's all I need)
Thermaltake Armor case
Vista Ultimate 32-bit

The CPU temperature will get hot while booting. By the time I've logged on to Windows, the temperature (as reported by both the ASUS Probe utility and Core Temp) is 85-90C. However, within about 90 seconds, it cools to a much more reasonable 35-45C, and generally stays there.

I built this to be a file/print/media server, so the case *does* have five drives in it, which I suspect might be interfering with airflow. However, if that were the case, I would expect precisely the opposite behavior - i.e. increasing heat as the system runs, not the other way around.

I'm on the verge of ordering a decent CPU cooler, but was curious if others had noticed similar behavior. Any advice?

Thanks,
-David

Have you tested load temps with prime95 (or similar)?

So, as it turns out, the problem was with the mounting of the CPU cooler. I realized that to install that Zalman would require removing the motherboard (the Zalman was beefy enough to require an anchor behind the motherboard). I wasn't too enthusiastic about doing that, so I took the original (stock) CPU cooler off, cleaned off the thermal grease, re-applied a fresh batch of grease and put the stock cooler back on. The CPU temp now stays in the "normal" range regardless of load on the box, or the ASUS EPU-6 engine setting.

Thanks to all for your suggestions!