If turning your computer completely off and back on again has not solved your problem, try some of the suggestions below.
If you have an error message, try typing the exact error message into Google. Chances are someone has had a similar problem and has posted a solution.
Is the problem specific to one document? For example, if you cannot open a Word document someone emailed you, but you can open other Word documents, the problem is likely a corrupted document.
Is the problem reproducible? If so, document or write down the sequence of steps that cause the issue. Try contacting the appropriate vendor for help.
If you suspect a hardware problem, see if
your hardware is under warranty.
If it is, you can probably get the problem fixed for free.