I have not had to do this myself, but as I routinely see questions about removing and reinstalling Sharepoint , I thought posting instructions provided by Microsoft CSS may be helpful to someone down the road!
Generally speaking, if you want to completely reinstall companyweb on SBS 2003 SP1, you need to follow the article KB829114 below, but it might ask you to insert the SBS SP1 CD3, so you need to extract SBS SP1 installation folders, and then point the SBS Integrated setup program to the folder for the ‘SP1 CD3’ contents.
The extraction process is listed below, please do follow the exact steps or the extracted files will be removed:
1. Start a cmd prompt and change directory to the SP1 download folder (or the SBS03_SP1 folder on PKG_CD2).
2. Then type “<path>\SBS2003-KB885918-SP1-X86-ENU.EXE /x” (with no quotation marks) and press Enter.
3. Specifying a path for the extracted files (such as C:\SBSSP1)
4. Run the SBS Integrated setup, and when the setup program prompts for the CD3, point it to the folder created above.
829114 How to remove and how to install the Windows Small Business Server 2003
As I know, we are able to keep the original SharePoint database and connect it to the new installation. If the original database is not corrupted, you may manually backup the files and then reconnect the database after reinstalling the components:
829113 How to restore a Windows SharePoint Services CompanyWeb database after
827701 How to perform a disaster recovery operation of SharePoint Services
As I know, on SBS 2003 we have a document which can make a full backup and restore for the whole system. It might be useful to you, I suggest you have a look at it:
Backup and restore SBS 2003:
Charles Yang (MSFT)
Microsoft CSS Online Newsgroup Support