How would you decrypt a MD5-encrypted string? ;)

Update: MD5 is one-way hash, and therefore, you aren't able to "decrypt" something you "encrypted" with MD5. This can be useful for passwords (and some operating systems use MD5 for their password file). You make a MD5 hash of the password once and store that output. When, later, a user types in his/her password, you MD5 that string too and compare the results. But since you specifically spoke about decrypting, this type (MD5) doesn't seem valid here. (Thanks to Limbic~Region for pointing out the lacking explanation)

Update: changed terminology a bit