My Dell Inspiron 530...

You cannot spend $200 on a video card with your current power supply.  If you have the Q6600, you may have the 350W PSU which would of course be much better than the 300W.  Depending on when you purchased your system, you may or may not have the better power supply.  You will need to open up the side panel and look at the sticker information on the side of your power supply to confirm.  The 350W will have one 6-pin PCIe connector for more powerful video cards.  The 300W will probably not.  You will see this cable hanging down from your power supply unconnected. 

Staying with ATI, you can look at the HD 4670 if you have the 300W and the HD 4770 if you have the 350W. 

Thanks alot, I heard sceptics about two cards,

( I run on 1920 * 1200 btw) I opened my case and my DCoutput(Ithink) was 350 Watts.

I read that the Raedon 4670 will do better than the 4770 because its 1gig ram? and i also heard that 4670 is all around better so whats your oponion?

thanks alot for the comment.

PS. Will this card run GTA IV on high settings at 1920 * 1200 with a reasonable framrate.?

The 4670 will not do better than the 4770 just because it has 1GB of video ram even though the game likes VR.  The 4770 is the much better card.  However, you will not be able to run the game at that resolution on high settings with either card and the 4770 won't run the game on very high settings with just 512mb of VR.   If that is your goal, then you are in for a power supply upgrade and a higher-end card.  This chart shows only medium settings with no AA.  For high settings, you will have to be looking at cards like the HD 4870, HD 4890, HD 5850 and all 1GB cards of course.   Your least expensive option is the 1GB GTS 250.

I read that it needs 450 Watts.. ( the Nvidia 1GB GTS 250) will my PC still run it..? or should i upgrade my power?  how easy it is to upgrade my power.. is it complicated? im not a computer wiz. thanks alot for answering my questions btw.

It is not difficult to replace your power supply.  HERE is your maual for doing it.  Here is a chart on power supply consumptions. The HD 5770 does not seem to use much more power than a 9600GT that I ran on my 350 watt power supply without any problems. 

Ok mate, so all in all in all out. Do you think I should close the line and buy a 5770, will it run good on 350 wats? will my computer crash? I've never modified my computer before so i don't know. thanks.

Just a litle bump, sorry.

You can give it a try.  If you experience things like game crashes, bad game performance, freezing during games, or computer shutdowns, then you know that your power supply is just not up to the task.  My concern would be the amp requirement.  I am not sure, but I think the requirement suggested is 40 amps and you may only have 25 amps on the 350 watt power supply.  Again, the card itself does not need 40 amps.  A 40 amp power supply is being recommended for the entire system by the manufacturer.  This seems really high to me though for this particular card.  However, if you are going to be pushing it with high resolutions and high game settings, I would consider a power supply upgrade.