Most 401(k) trustees have a minimum size requirement to continue holding a 401(k). Presumably yours is in excess of this (usually $3000 or $5000), else they would have issued it to you over a year ago.

You can choose to leave the fund with its current trustee, or you can request that it be rolled into another 401(k) (if you have a new employer and the new plan allows it), or you can roll it into an IRA.

The job that I left five years ago had its 401(k) with Fidelity. Since that is also where I have some other retirement money, I decided to leave the 401(k) where it was, as it was. It just doesn't get any further contributions.

It depends on the balance. If the balance is less than $1000 your balance could be forces out of the plan, but this would normally happen in the same year that you terminated. Since it's been 2 years since you worked there, I'm guessing your balance was higher than that.

The answer to your question is that the money just stays in the plan until you withdraw it. You can leave it there for retirement or take a distribution.

If you leave it, you should be contacted in the year you become age 70.5 to start taking annual withdrawals.

If you want to take a distribution, contact your employer or the plan record keeper to start the process. Be warned, however, that you want to do a "rollover" to another 401(k) plan or IRA to avoid taxation in the year of the distribution.

Assuming your balance is high enough to meet your provider's minimum, nothing should happen. This goes for taxation purposes as well, since 401(k) plans are tax sheltered until you reach retirement age. Unless you roll it over, you simply won't see further personal or employer contributions into the account, and you may see a slight fee deducted every year by the institution managing it.

If you're not particularly attached to the plan or the provider, I recommend having it rolled over into a personal IRA or 401(k) provided by your new employer. This makes sense for consolidating your accounts and maximizing your growth potential. The rollover process is fairly straightforward. You should be able to find out specifics from either your old 401(K) provider or your new one.

To really get a fresh start on long term investing, pick up a few good books that will help you allocate the old 401(K)'s resources more effectively. The Bogleheads Guide to Investing is #1 on my list.