There are many techniques of troubleshooting which don't require erasing a hard disk, and eliminating the probable cause of a software issue. Some just require creating and logging into a new user to eliminate the issue with Apple menu -> System Preferences -> Accounts in Mac OS X, or in prior Mac OS versions Apple menu -> Control Panels -> Users and Groups in prior Mac OS versions:
1. Preference issues.
2. Font issues
3. Cache issues
The above could also be system wide issues too. The below are system issues which can be isolated without erasing:
4. File sharing port assignment issues and other administrative issues.
5. Directory issues.
6. Driver issues.
7. Firmware issues.
8. PRAM issues which can also relate to clock battery issues which may appear when your system is older than 3 years.
Regardless of what is the cause none of these requires an erase of your hard drive to isolate. Only when you have eliminated the above 8 issues, and your data is backed up, would you want to erase your hard drive. Which brings me to another point, you should be backing up your data all the time when there is something important you want to keep.
If you need help with any of these processes, or understanding how to eliminate those as a possibility, ask in the appropriate forum, and someone here should be able to help you out. Never assume that an erase is necessary to solve your problem unless you have eliminated all other possible causes. You would not want to unnecessarily have to rely on recovering your backup unless all other software related issues have been exhausted as possibilities and you want to see if hardware is the actual issue.