Ok, to explain, I believe I have a more powerful system than the recommended system specs state to play this game while it looks good. 

And yet my system can't seem to run this game without most settings being on low or off without the game being rediculously slow and the shadow beings drawn incorecctly. 
(My system can play Crysis on high for as long as I want, but Borderlands is a different story.) 
By the way, I have borderlands on steam due to the 66% off offer recently. 
Also, I've worked really hard to make sure my system is totally updated.
 
The recommended system specs required to play this game while it looks good are as follows: 
 
OS: Windows XP/Vista
Processor: Intel Core 2 DUO @ 2.4 GHz / AMD Athlon 64 X2 4600+
Memory: 2 Gb
Hard Drive: 8 Gb free
Video Memory: 1 Gb
Video Card: nVidia GeForce GTX 260 / ATI Radeon HD 4550
Sound Card: DirectX Compatible
DirectX: 9.0c
Keyboard
Mouse
DVD Rom Drive 
 
My system specs are as follows: 
 
OS: Windows XP service pack 3 
Processor: AMD Phenom X4 9950 2.6GHz 
Motherboard: MSI DKA790GX 
Memory: 4GB 
Hard Drive: 230GB 
Video Memory: 1GB 
Video Card: ATi Radeon HD 4870 
DirectX: 9.0c 
 
The rest is unimportant for this query. 
So I want to ask anybody who feels they can contribute, why is my system running really slowly for Borderlands, as it should realistically be playing at near enough full system settings at a steady 30-60 fps. 
What do you think I can do about it? And/or What parts do you think I should buy? 
This is getting on my nerves because a friend has just bought a new setup that can play it really well and we were just planning to go running into the Pandora desert guns blazing and laughing maniacally. 
Instead he's doing all the laughing, and all I can do at this moment is splutter and gurgle.

What OS does your friend run? 
A quick google search got me a Tweaking post that might get some more performance out of your Borderlands, but looking at your specs there is something seriously wrong if you can't run Borderlands.
 
Have you tried posing your question to the official Borderlands site?

"What OS does your friend run? 
A quick google search got me a Tweaking post that might get some more performance out of your Borderlands, but looking at your specs there is something seriously wrong if you can't run Borderlands.
 
Have you tried posing your question to the official Borderlands site?

"

The standard answer is "upgrade all drivers" (esp video card, mobo, audio, directX). 
The next thing I'd do is disable all network connections and then disable your anti-virus + firewall.  (Disabling network is for safety; antivirus + firewall are what we really want to test since they can sometimes interfere with syscalls or hdd usage).

Yeah try your drivers. No need to turn off anti virus unless you're using a crappy one.
 
Also, WinXP might not be able to handle/show all your RAM? I don't know what the max is for XP.

A lot of the current ATI drivers make this game run very strangely if you have Catalyst A.I. enabled. Try disabling that first, if that doesn't work, update to the most recent drivers, disable A.I. again, and try.