You can try doing it in Safe Mode. Might make a difference. If it still doesn't work, find another free antivirus like Avast or Avira. They are considered to be better than MSE.
Trying to install Windows Security Essentials on my Acer Aspire 5610
"Please wait while this wizard in stalls security essentials on your computer. This might taks a few minutes"..... ummm it has been four hours so far......