You say they are temp files and refer to cookies. Which are they?
I have found there are files you cannot delete. I have deleted the directories in "temporary intenet files" - only then do some files vanish. They appear to be the "dated" internet history. The folder is not a normal folder though I have not tested it's attributes as "system". I use a free product called Xteq (xtec.com) that allows (many many) things to be set-up one of which is displaying the file attributes in WinExplorer. Not sure about folder attributes.
I also use a free prog (not downloadable any more) called System Suite that lists all temp files and all cookies and seems to get rid of those I tell it to. I would guess Norton do a similar product. I have stayed with Win98 mostly to give access to DOS and freedom to upgrade H/W.