Magento

I have upgraded magento from version 1.6.2.0 to 1.7.0.0 with following steps.

./mage mage-setup
./mage sync
./mage upgrade-all --force

But when I open index page in browser it takes to installation page. There is start download process button, I clicked that button , new button appears \"continue magento installation\” but when I clicked that button it remains on same page.