If it truly is an "old" 401(k), please explain why you can't move it. Or did you mean that you can't move your other 401(k)?
At your age, I doubt an annuity is really what you should do, but it is a possibility. Other possibilities are a stable value fund, a certificate of deposit, maybe some US Treasury bills, etc all of which would be more than somewhat safe. Why pay the expenses of an annuity and saddle yourself with the early withdrawal problems?
In essence, you roll over you old 401(k) into an IRA and select the investment(s) that fits into your overall portfolio and asset allocation plans. You may also wish to read the thread started by dex "Going to 100% cash".