I just recently started up my PC which runs Windows 7 64bit on an Intel Quad 2.4 processor (asus P5q motherboard), with an Nvidia 9800GTX card... I started to get these weird artifacts and lines on the screen... flashing in and out and the computer sort of freezes up while this is occurring. I was wondering if someone could confirm if this is a graphics card issue, whether or not it should be replaced or if this is another sort of problem?  It also shows some fuzzy colours as the artifacts... I  can post more screens if needed but was wondering if I should just pick up a new graphics card?
 

Do you have these artifacts when you boot up your PC, before getting into Windows? And do they appear after a while or does it always look like that?

use a monitoring program like Rivatuner or MSI afterburner and see what your temps are like.   You might have a faulty Fan, if it's overheating.  

Do you have these artifacts when you boot up your PC, before getting into Windows? And do they appear after a while or does it always look like that?

Yeah, the guys are right. It's almost guaranteed that it's the graphics card and if you've got the artifacts directly after booting (in dos and in your bios) it's pretty much permanent (there is a way to fix that though).

Edit: Alright, you should check your temperatures just like @Marz wrote and try to borrow a graphics card from someone you know to really make sure that the card is broken. When you are 100% sure and are thinking about buying a new one you can do this http://www.addictivetips.com/hardware/fix-your-graphics-card-by-baking-in-oven/. I've done this 2 times already and it worked both times. <- once again: ONLY DO THIS IF YOU ARE 100% SURE THAT THE CARD IS BROKEN AND THAT YOU DON'T CARE ABOUT WHAT HAPPENS TO IT. I can't guarantee you that it will work, so.. it's your decision.

Artifacts normally means that the GFX card is on it's last legs. 
 
 The GTX 460 is alot better than a 9800GTX+

The card is dying, simple enough. If you have an EVGA card that you registered on their site you can get a replacement for free. Personally i've done this and they kept sending me shitty cards that failed after a few weeks or a few months and went to a GTX 560 ti.
 
The oven bake trick works but is only a temporary solution, so if you have no warranty and you have no money for an upgrade now; it's a good option.

If you have any interest in playing the new Deus Ex, AMD is including it for free with their video cards now.

Thanks for your help guys, I decided to just purchase a new card so I got the radeon 6670. It's a bit better than the 9800GTX (which was the source of my problem), and includes Direct X11 support so Metro 2033 looks outstanding. Now I have much anticipation for BF3's DX11 support...ohh man.