How do I reverse a transaction? Ok here is the thing I lost coins on this computer trying to send them to my laptop this is what it said

Status: 0/unconfirmed
Date: 2/6/2013 14:53
To: 1PrM4QW3UtkGhi1uXFjvtDhn3h3x3pMipn
Debit: -3.98
Net amount: -3.98


How do I reverse it or stop it its been over a month and I cant seem to find how to do it.
You didn't lose them, they were successfully sent. You can see the confirmed transaction here, included in block 219,976.

In fact, the recipient spent them (sending them to 1ESTZpJUkqSQDkjyQHYAFecasEykhFWmMj) about 9 hours later.