Only New Products showing in Category Pages

Question

I've Fresh Magento installation. I've added magento sample data into db, and installed magento using that DB. It didn't show any products into category page. After several hit and tries I figured out that if I mark a product as NEW, then it starts showing up. I've tried different methods to get rid of this problem, but nothing seems to work. This is what I've tried doing:

• Reinstalled my Windows 7
• Fresh installed xampp
• Fresh installed magento
• Connected it with Database of dummy data
• To check if the problem is with my theme, I've used default theme

I've checked the checklist on this stackoverflow asnwer, but still have the problem. The problem is not only confounded to category pages, only the products who are marked as NEW will display in 'related products' block, and on homepage. As if products which are not marked as NEW are invisible.

Can anyone please point out what could be the possible problem.