Pfizer Inc., New York, hired Fidelity Investments as record keeper of its $7.8 billion 401(k) plan, said Jennifer Spendlove, an investment officer. Ms. Spendlove would not say what firm Fidelity is replacing. According to the Money Management Directory, Pfizer's record keeper was Hewitt Associates. Kelly Zitlow, a Hewitt spokeswoman, did not return calls by press time. The administrator is Northern Trust, and several firms provide investment options.