Error 5

I've been using bleachbit for a while w/o problems, but I noticed in the last month or two that several {Error 5] instances occur, and several files in the "C:\WINDOWS\temp\" cannot be deleted.

Example:
[Error 5] Access is denied.: Command to delete C:\WINDOWS\temp\tw-****************.tmp

Similarly,there is this specific error:
Error: system.tmp: Command to delete C:\WINDOWS\temp\WebInstaller

Any help to solve these errors would be appreciated.

Thank you!