Hey guys!
I went around Googling for a tech forum where people can help me out with upgrading my computer, and i stumbled across this site!

Anyway, on with what i came here for. To be honest, i'm pretty incompetent when it comes with computer hardware, kind of dropped the ball on that one.
Making matters worse is i really need to upgrade/buy a new computer, because currently i believe my computer is fairly out dated and slow for my purpose.

My computer's Purpose:
I do a lot of graphic design work, im finishing school this year and will be using it more when i go to university next year while studying Multimedia/graphic design.
I pretty much always have Photoshop running in the background/using it, windows media player runs constantly, Dreamweaver is usually open as well, sometimes with Maya as well, and of course Firefox with various other programs and folder directories. So i have a lot of programs running simultaneously.


Current specs:

Basic specs:
System: Dimension 8400
Manufacturer: Dell, Inc.
Processor: Intel Pentium 4 550, 3400 MHz
Memory: 2560 MB (DDR2 SDRAM)
Video: RADEON X800 XT (256 MB) x 2
Mother board name: Dell Dimension 8400
Mother board chiptset: Intel Alderwood i925X
OS: Windows XP, SP2
Monitor 1: 17" Dell LCD
Monitor 2: 21" LG LCD
HDD: 150gb

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Specs in detail:
Motherboard:
CPU Type
Intel Pentium 4 550, 3400 MHz (17 x 200)
Motherboard Name
Dell Dimension 8400
Motherboard Chipset
Intel Alderwood i925X
System Memory
2560 MB (DDR2 SDRAM)

Graphics Processor Properties:
Video Adapter
ATI Radeon X800 XT PCI-E (R423)
GPU Code Name
R423 (PCI Express x16 1002 / 5D57, Rev 00)
GPU Clock
500 MHz (original: 500 MHz)
Memory Clock
500 MHz (original: 500 MHz)

Display:
Video Adapter
RADEON X800 XT (256 MB)
Video Adapter
RADEON X800 XT (256 MB)
3D Accelerator
ATI Radeon X800 XT PCI-E (R423)
Monitor
Dell E173FP [17" LCD] (F504545E3J6U)
Monitor
Plug and Play Monitor [NoDB] (1801352110) <-- This should be my LG 21"

[ Memory Devices / CHANNEL B DIMM 0 ]
(I HAVE TWO OF THESE 256mb INDENTICAL)
Memory Device Properties:
Form Factor
DIMM
Type
SDRAM
Type Detail
Synchronous
Size
256 MB
Speed
533 MHz
Total Width
64-bit
Data Width
64-bit
Device Locator
CHANNEL B DIMM 0

[ Memory Devices / CHANNEL A DIMM 1 ]
(I HAVE TWO OF THESE 1024mb INDENTICAL)
Memory Device Properties:
Form Factor
DIMM
Type
SDRAM
Type Detail
Synchronous
Size
1024 MB
Speed
533 MHz
Total Width
64-bit
Data Width
64-bit
Device Locator
CHANNEL A DIMM 1

CPU Speed:
CPU Clock
3391.6 MHz (original: 3400 MHz)
CPU Multiplier
17.0x
CPU FSB
199.5 MHz (original: 200 MHz)
Memory Bus
266.0 MHz
DRAM:FSB Ratio
8:6

SPD Memory Modules:
DIMM1: Kingston
GB DDR2-667 DDR2 SDRAM (5-5-5-15 @ 333 MHz) (4-4-4-12 @ 266 MHz) (3-3-3-9 @ 200 MHz)
DIMM2: Kingston
GB DDR2-667 DDR2 SDRAM (5-5-5-15 @ 333 MHz) (4-4-4-12 @ 266 MHz) (3-3-3-9 @ 200 MHz)
DIMM3: Samsung M3 78T3253FG0-CD5
256 MB DDR2-533 DDR2 SDRAM (5-4-4-11 @ 266 MHz) (4-4-4-11 @ 266 MHz) (3-3-3-8 @ 200 MHz)
DIMM4: Samsung M3 78T3253FG0-CD5
256 MB DDR2-533 DDR2 SDRAM (5-4-4-11 @ 266 MHz) (4-4-4-11 @ 266 MHz) (3-3-3-8 @ 200 MHz)

Memory:
Physical Memory:
Total
2558 MB
Used
1530 MB
Free
1027 MB
Utilization
60 %

Swap Space:
Total
4450 MB
Used
2170 MB
Free
2279 MB
Utilization
49 %

Virtual Memory:
Total
7008 MB
Used
3701 MB
Free
3306 MB
Utilization
53 %


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I think thats most of the information that might be inportant, i tried adding as much as possible so someone can help me faster But im sure i put a lot of crap in there that wasnt neccesary. If any other information is needed please let me know, im using Everest to get this information.

My concerns:
I'm worried that my computer is already so far outdated, that upgraded hardware wouldnt run at optimal speeds etc.
I'm already concerned that my Motherboard cant run my RAM properly. The speeds that is, like the mHZ i think my RAM is 667 and 533 but my mother board is only 200? Or is that something im not reading into right?
What's this story with Sli and things like that?

What i want:
I need a computer that can handle running multiple multimedia programs simultaneously without lagging too much.
Definately dont want it to crash!
It doesnt neccesarily need to cater for gaming, though it would be nice to have the option of playing a game now and again - currently i cant run the latest games ;(.
Need a lot of RAM.
Need a massive HDD.
Helluva lot of advice =D

And obviously i want the cheapest option - but i dont want to neglect neccesary quality products which may cost a little more.

I'd really appreciate someone letting me know what situation im in right now.
Ultimately i really want to know:
1. Will it be worth it to upgrade?
1b) What do i need to upgrade?

2. Should i just purchase a brand new computer?

3. Should i purchase a stock computer, and upgrade that?
3b) Whats the best way to start?

Thanks so much to anyone even taking the time to read this!
Would really appreciate all the help i can get.