First of all, You would need a program by the name of Eggcrack.
It can be found on these forums.
The only problem is, Cracking a SINGLE ACCOUNT Would take somewhere from 1 day to like a month, With very good internet, And about 10k+ WORKING And FAST Proxies.
You would also need about a 500,000 Password list, And cracking someones account specifically is kind of a dick move, Unless it is for a good reason, In this case, it is not.