Speak about specifics that relate to the position you are applying for. If you do not have specific experience, get as close as you can.

If you are being asked this question from your employer then you can explain your experience. Tell the employer what responsibilities you were performing during your job. You can tell what programs you developed and what modules you worked on. What were your achievements regarding different programs.

I have been working with computers since 2001. I also have a degree in network support/computer repair. I have built my last 3 computers, have work with Dell as an employee. So I have around 15 years experience working with computers.