Modify (Upgrade) or Replace Sony Desktop?

[NCPRIUS]

I have a Sony Desktop Model VGC RA842G running Vista Premium w/SP1 (more specs below) which is about three years old. What can I replace to make it even more robust (say for video editing, etc.)

Main Circuit Board
Board: ASUSTek Computer INC. P5LP-VX
Bus Clock: 200 megahertz
BIOS: Phoenix Technologies, LTD 1001 05/18/2005

Processor3.00 gigahertz Intel Pentium D
16 kilobyte primary memory cache
1024 kilobyte secondary memory cache

Memory Modules
2046 Megabytes Installed Memory (Maximium possible under current configuration)
Slot 'A0' has 512 MB
Slot 'A1' has 512 MB
Slot 'A2' has 512 MB
Slot 'A3' has 512 MB

3 Hard Drives with 1.25 TB capacity

[Accessless]

Hmm strange, it looks like the main board is a custom build for Sony. The closest match that I can find is the P5L-MX. http://uk.asus.com/products.aspx?l1=3&l2=11&l3=194&l4=0&model=1320&modelmenu=1

Are you using the On-board graphics adapter (i.e. the one built into the main board itself). If so then a dedicated graphics card could be the answer.