First, be sure you meet the minimum system requirements for Dark Age of Camelot as well as Windows XP. If you meet the requirements for both, you may perform the following, but be aware your system may become unstable in which you will have to revert to the default settings. Right click my computer, click on properties. Click on Advanced. Under peformance, click on settings. Under visual effects, select "adjust for best performance". Under the advanced tab make sure "programs" is selected for the processor scheduling and memory usage sections.
Also, please make sure that you do not have any anti-virus or other intensive programs running in the background.