Its a common problem if u running pirated WinXP. Do a google search for the file u need + download (FILENAME.DLL + download) to find sites offering the file outside of windows updater. When you download the .zip file you unpack it using WINZIP (free download) and EXTRACT into your everquest main folder on your c drive. If all goes well it will extract there and maybe even ask you to if its ok to replace an old file of same name. Yes of course and then restart the eq patcher (hopefully) you have also checked in ADVANCE on the patcher and checked off any other optional downloads from all your bought expansions, etc and fully checked your files using the patcher's extra functions.
Eventually Microsoft will make all their changes such a P-I-A to keep up with that most will have bought versions of XP on their comps or the courts will nail em with another anti-monopoly charge forcing them to remove some of their illegal practices. Hehe I am too noobish in the dark arts anyway to know anymore than that at this point.
Hope this helps ya some....catch ya in the game!