400W Nvidia GeForce 9800 GT Compatible with Vostro 420 (350W)?

Dell offer the GeForce 9800 GT as an option for the Vostro 420.... Will I have any problems if I purchase this system?

No, as the entire system would use less than 240 watts with the 9800 GT and the 350W power supply would be capable of handling over 400 watts.

OK,

Thank you JMichael for your answer. I would need some clarification please :

The GeForce 9800 GT uses a max of 105W by itself (according to specs). So what you say is that the other components use around 135W (240W-105W=135W)?

Why is a 350W PSU capable of handling over 400W?

That's about right.  The only thing that uses a more significant amount besides the video card is the CPU.  Everything else uses a small amount such as the hard drive, optical drive, memory modules, etc.   Dell tends to use pretty good quality power supplies and rated for continuous output meaning they can run at their maximum and usually higher without any problems. 

Alright,

Thank you so much JMichael for your help! It's very much apreciated.

Have a nice weekend!

Ummm...  No.

1:  A 350 watt power supply can supply 350 watts, no matter WHO makes it.  Using your logic, it would also hold true that if you have a 100HP engine in your car, then you could safely pull 125HP from it, just because it says BMW (...or insert your favorite engine brand name here...) on it.  That is COMPLETELY wrong.

2:  Dell uses the cheapest power supplies that they can lay hands on.  I have a customer that has a 420, and it came fromthe factory just the way you would think...  Quad Core, four 1T hard drives, multiple USB powered devices, dual 24" monitors, and the 9800 graphics card, all runing off that 350 watt supply.  The stability issues and problems were never ending.  I replaced the MoBo once, and the power supply THREE TIMES...  T H R E E times...  before I was able to make them listen to me tell them that they were overloading the original PS, and they finally sent me a 600 watt box.  Now, 600 watts is most CERTAINLY more than the system needs, but I have never been back to the customer's house.

All I can say is that I HOPE that you didn't buy the box without upgrading the PSU...

Sorry, but your point 1. is incorrect. The Dell power supply is rated 350W continuous output. That's not the peak rating. It can supply more than 350W. To try to use your example: it's like a 125HP car engine that's been labelled as 100HP because having it at 125HP all the time is a bad idea.

I've installed/used nVidia 9800 GT cards in Optiplex 745/755s, and they are fine.