Each 401(k) plan has different rules about when you are allowed to take money out, withdraw, rollover, or transfer the balance from your account.
Most 401(k) plans only allow you to take money out of your account, either as a withdrawal or rollover, if you are at least 59.5 years old or if you are no longer employed by your company.
Download the Summary Plan Description under My Documents to see what kinds of distributions your 401(k) plan allows.