Need some techie info please guys.

At the moment i'm running the following system:

Mobo - Gigabyte 7VM400M-RZ
Processor - Sempron 2.4 running at 1.6ghz (socket A)
Ram - 512mb of DDR 333
HD's - a very old Maxtor 10gb drive for windows xp and a seagate 160gb for video etc.
Gfx card - Geforce FX 5200

In the past this has been fine to edit on but during my last project it was very sluggish, multiple rebbots etc.

I was considering simply replacing the old maxtor HD which im sure is a major sorce of slow down ect with a new drive say 80gb, and adding 1 or 2gb's of RAM to replace the old 512mb

BUT

as happens when you start reading up on pc technology you find out that you've been living in a cave and that all your gear is out of date!!

So i'm thinking of a total upgrade pretty much, keeping my gfx card and 160gb HD an possibly the processor but upgrading the rest.

I have been looking at the Shuttle mini pc's as i travel quiet alot but really don't want a laptop. Any one have any experience of these?

also my main problem is possibly choosing a new processor, i'd want to stick with AMD but do i go for socket 754 or 939 and is socket A that out of date? It seems to be if you want a mobo with SATA compatability which most Shuttle mini pc's use.

cheers for any info, espeically on the processor sockets thats where im lost.

Max