Using XP and MS word 2003.

Purchased a Dell computer which came pre-loaded with McAfee Security Center. After 6 months or so, had to do a system restore because of an operating problem. When the system was restored, all of the components of McAfee were not restored. Now, when I boot, I get two error messages indicating that McAfee is not working because some McAfee files are missing.
Tried to remove McAfee by using add/remove and cannot remove it because files are missing. Tried to download Security Center from McAfee website and that service is no longer availabe to me, since I have owned the computer too long. Purchased a new Security Center, hoping to load in all the files, thereby getting the missing files. Cannot load in new Security Center because there is an old security center already in the computer. I am told to remove the old one, using add/remove, which I cannot do, because of missing files.

What in the heck do I do now?