Ah the dreaded Dell generic poor quality PSU, most if not all of the branded names are guilty of this as it keeps build costs down, they don`t care when they`re sold they then try and sell the same inferior quality replacement parts to the poor customer.
I am thinking it is your PSU being weak that is causing this and this would seem to be supported by some info I have looked at, I know you are in the UK but if you need to know details about a potential purchase use the Newegg site to get the required info, I have just picked out a random model of your card; http://www.newegg.co...5-295-_-Product
clicked on the details tab and it tells you that a minimum 450W PSU or Greater is needed to support the card.
Your specs says Nvidia Geforce GT220, that is the GPU manufacturer but not always the actual card manufacturer, does your GFX card have another brand name on it such as Sparkle, Palit or Gigabyte for example, if you let us have this info we can look into the cards PSU requirements.
Edit: Additional info, looked at 2 other brands of your card and got different PSU requirements.
Requires a minimum of 300W leaving you with 50W headroom;
Requires 350W leaving you with no headroom; http://www.newegg.co...0-446-_-Product
Dell have most likely fitted a card that requires 300 or 350W, that would be bad enough even if they used a good well known brand of PSU such as Antec or Corsair.
Edited by phillpower2, 09 January 2011 - 05:29 AM.