ATI cards have more compatibility problems with some Intel chipsets and most VIA chipsets, particularly from older mother boards. If that board uses the Intel 845 chipset, you have to realize that was designed in 2004 and will perform less than ideal with most modern video cards.http://www.intel.com/support/chipsets/sb/cs-009236.htm
Recommendation is to get your money back on the video card, then get a used 8800 GTS 640 or 320 off of eBay. That will increase your gaming performance from on-board video and is more likely to be compatible with your Chipset. It is not as nice as the HD 5770, but you can't expect to use something that new on an older board without having problems.
Depending on which Intel Celeron you are using, that CPU will bottleneck a 5770 severely anyway.