Linux slower than Windows

Hi,

Now that I've got all the Linux proponents all worked up, here's my story:

During the past week, I upgraded my main PC on which I run Win2K. According to BoincView I got about 11.2 credits/hr running W2K on the pre-upgrade machine (AMD64 3000+).

After the upgrade I used the AMD64 3000+ mobo and chip to build a machine on which I installed Fedora Core 4.

Now BoincView shows that the credits/hr dropped to about 6.7.

Why this dramatic drop? The only differences are going from a 160GB to 40GB HDD and from 1.5GB RAM to 256MB. Surely that can't be the cause of such a dramatic drop in performance? It's more depended on the CPU than anything else if my logic isn't flawed?

I've seen this drop in actual credits/hr processed as well.

Any suggestions for a Linux novice?

Thanks!

V7