OK ..
Here;s the last official one from Dell:
http://support.dell.com/support/downloads/download.aspx?c=us&cs=19&l=en&s=dhs&releaseid=R66756&SystemID=INS_PNT_P4_5100&servicetag=7DH6L31&os=WW1&osl=en&deviceid=2552&devlib=0&typecnt=0&vercnt=2&catid=-1&impid=-1&formatcnt=1&libid=6&fileid=86672
There is probably an update generic from ATI, but this is the last published one from Dell.
Give it a shot, and if I find anything newer, I'll let you know.