401(k)s are like IRAs, solely for individuals. She can, however, roll to an IRA so that she has many more options in investing the funds. If your income is less than $150k, you can also contribute to a deductible "spousal IRA" for her each year. $5,000 limit for 2008.

Feel free to email if you want to discuss!

it is not legal.
u , no she must open an IRA and 'direct rollover ' to her IRA.
no one can co-mingle 401k or ira.
never ever mix into an other 401k - lots of legal penalities even if trying.

the IRS simply doesn't allow it, other posters have provided options

401k's are funded with untaxed money and the IRS wants to keep track of who owes what. So, no mixing funds with somebody else's money and sometimes not even your own(don't mix it with a Roth IRA because a Roth has already been taxed).

The 401(k) is tied to a person so you can't combine them.
But you definitely should open a rollover IRA with Etrade or some other discount brokerage and move the money there. Then you have control over it and have lots of options on how to invest it.