Dp4.5, Latency, Stuttering Issues, using mac mini as a DAW: good or bad? Options

[willie63]

I was wondering if someone can enlightened me on an issue I am having with my system.
Currently I am using a mac mini 1.42 ghz, 1gig of ram with m-audio mobile-pre usb audio interface and an m-audio 4x4 usb midi interface.
For software I use DP4.5 with Reason 2.5 and the Garritan Personal Orchestra, a virtual symphonic orchestra using the kontakt player.
I created a file (song) with minimal problem. That minimal problem would be these pops every couple of seconds during playback. I would remedy this by changing the Audio hardware setup in DP4.5 between medium and low or changing the buffer size from 512 to 1024 or back to 512 when the problem re-occurs.
The problem gets worse when I created a new file. I would open some new midi tracks for the garritan instruments (4 tracks) some midi tracks for my modules and for reason. When looking at my CPU performance monitor, it reads at about 75% to 90% usage and a latency issue comes to play. The thing is the tracks are blank!
Is 1gig of ram and a processor speed at 1.42ghz not enough?
The GPO requires 2 GB of free hard disk space. I have 30gb of free space.
A mac G4 at 1.25 MHz is minimum but may not load the full orchestra, and 1 GB of RAM or more is needed to play entire orchestra. I'm not using the full orchestra.
What could be the problem? Any help would be deeply appreciated!!!

Willie63