If your Magento search is indexing all products on the search results page and the search filter is not working as you need, then here is the solution :
- Goto your template folder, app/design/frontend/default/your-theme/
- Here you will find a folder called /template/ . Inside it another folder will be there, /catalogsearch/
- Just rename it to /catalogsearch.bak/
- Now goto app/design/frontend/base/template/catalogsearch/ . Copy this folder and copy it to app/design/frontend/default/your-theme/template/
- Also copy catalogsearch.xml from app/design/frontend/base/layout/ to app/design/frontend/default/default/layout/