|Useful tips/advice for sure above.|
Most definitely make copies of all those important files and "stuff" on the hard drive "now". Copy to optical media and verify the discs can read properly on both your system as is, and if possible another. This in-case the hard drive is starting to fail; and clicking noises often often come from a drive starting to fail - mechanically at least.
Always wise to have files duplicated off the system in-case of system failures at any time.
Note I suggest copy not backup... A true backup is not the same as copy. The former is routine that is in "code" and not easily viewable as data on any system - without it is "installed" (restored) there. A copy is just that and can be read etc. on any system that can the read file format etc. - straight from media it's on.