Did you enable the ReIndex option when you ran housekeeping? That is not enabled by default so please try using that option.
The PostgreSQL.conf file isn't available through the Start menu for PostgreSQL versions after 8.3 but you can open it manually (using Notepad or any other plain text editor) from the folder:
C:\Program Files (x86)\PostgreSQL\8.4\data
If you use Windows 7 or Vista you will need to open Notepad by right clicking and choosing Run As Administrator in order to be able to save your changes.
If you continue to have problems with that hard drive, you should consider replacing it.
"it" refers to your hard drive. Sometimes this kind of error can indicate bad sectors on a drive, and that can mean that the drive is deteriorating.
Try running
chkdsk to see if there are any problems with your drive. If there are, I'd suggest making a backup of any important data somewhere other than that drive (I'd suggest you do that anyway - even new drives can fail at any time without warning).