Upgrading Help Needed!

Hello, i've finally got my new computer to work that my uncle has built me... I've discovered that I have no soundcard (or so it seems) crappy 32mb video card, and 224mb of RAM. I want to upgrade so badly but I don't know what to purchase. I've included a DXdiag to help figure out what I need...

My specs: (according to Everest ultimate)
Motherboard Name: Asus P4S800-MX (3 PCI, 1 AGP, 2 DDR DIMM, Audio, Video, LAN)
256 MB PC2100 DDR SDRAM
SiS 661FX (video card)
2.53ghz

So I picked this out of a local computer store site:
4 Channel Sound Card
OCZ DDR400 512MB Value RAM
(not sure of the video card yet) 64mb - 128mb though

Thanks for helping a noob.

BTW, can someone help me on how to enable my sound card so I don't have to buy another?

 

Cant help you enable your soundcard without knowing what it is but your motherboard has onboard sound,to enable your onboard sound go into your bios keep tapping del. at boot up then navigate the menus until you find onboard audio or onboard ac97 and enable,then download and install this driver

http://dlsvr01.asus.com/pub/ASUS/misc/audio/alc655/32b366.zip

and of course make sure your speakers are connected to to the onboard sound card output,check this manual,you usually have to connect your speakers to the green socket

http://dlsvr01.asus.com/pub/ASUS/mb/sock478/p4s800-mx se/e1918_p4s800-mx_se.pdf

MOTHERBOARD HOMEPAGE

http://support.asus.com/download/download.aspx?SLanguage=en-us&model=P4S800-MX SE

If you want to install the soundcard disable onboard audio in bios,connect your speakers to the new soundcard and install the latest drivers from the manufacturer of the soundcard