Hardware, Linux & AGE!!!

Hi all you,
I noticed after 3 years and half of use that my HDD is still working very fine, not bigg althought Graphic designing & Sound Ceation (for fun and wor also)require much space and make an abuse use of the drive.
It's ok till now::
since i installed Linux Mandrake8.0 i noticed another thing,,,the HDD is Slowing down
step by step it reached the edge and now it works too slow(i hate that)

My question is
1 [U]Is that a question of age!!!!Maybe my HDD should be changed???[/]
2 Maybe it couldn't handle the ob i was doing on it??!!Who knows
3 Is is Linux who uses excessivly the HDD???
4 Is it Formatting??!!I did that(complete format) about 5 time

Fans for taking care