conversion of sole proprietor into pvt co

This can be done by floating a new private company. There is no specified procedure for conversion given in the act because sole proprietorship doesn't have a separate legal status so the assets and liabilities of the sole proprietorship shall be considered as that of the proprietor. So converting a sole proprietorship into a private limited company is as good as floating a new private company.
One person company is recommended for the conversion of sole proprietorship into a company

The tax law provides exemption(subject to conditions)from Capital Gains on transfer of sole proprietorship to company.