Random program is not a valid windows image

I am running Windows XP. After logging in, I am getting an error message stating: “The dll or application C:Windowssystem32 (program that appears randomly) is not a valid windows image. Please check this against your installation diskette.” I am also getting the same message when trying to access any programs on my PC. Everything works well, but the error message just keeps on appearing after logging in to my computer. I will appreciate any help.
