Vista - update error 800700c1

i read through all the previous posts and tried all of the suggestions. my
only problem is that my computer will not allow me to change to run as an
administrator. the check box and wording is gray to where choosing it is not
an option. i also cannot pull up internet options. i get a box saying
"C:\Windows\system32\ADVPACK.dll is either not designed to run on windows or
it contains an error.", thus i cannot delete my temp internet files and my
defrag won't work. i'm thinking my computer has some serious windows issues
at this time. if anyone can help me figure out how to fix at least one
problem, i would be grateful! thanks!