Want to install the latest preview version of win10 What should I do if the SSD memory is not enough?

For various reasons, the SSD installed with win7 memory is not enough 20G, can not meet the requirements to continue to install win10, how to do?
1, first install a pirated version of the win7 system in the D drive, or genuine, The key is to have funds

2, then format the C drive, this time will lose all the data on the original SSD, including the original system

3, by opening the D drive system, Boot download win10 such as C drive

4, finally you can install win10 on the C drive

5, computer technology is generally not suitable for operation, otherwise win7 and win10 may not be installed properly