Powershares QQQ Trust, Series 1 changed its symbol from QQQQ to QQQ. If you don't want to lose your existing data for QQQQ, you can copy QQQQ.WL (typically located in C:\Documents and Settings\[user name]\Application Data\Fidelity Investments\WealthLabPro\1.0.0.0\Data\Q) and paste the copy back in the same directory. Rename the copy QQQ.WL, and you have all of your historical data attached to the new symbol.

Don't forget to change QQQQ to QQQ in all of your data sets also.

It's easier than that. You can use the Data Manager > Fidelity Data "Change a symbol" tool. This single action will take care of all of the above (for Fidelity data and DataSets).

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Well, QQQQ needs to show up in the Symbol Quarantine first. You don't have to wait for that, however, if you add QQQQ= (with the = sign) to the SymbolQuarantineList.txt file in the ..\Data\FidelityStaticProvider folder.

... oops, just found a bug. If you relocate data, the wrong SymbolQuarantineList is displayed. Consequently, for now, use SymbolQuarantineList.txt in the non-relocated Data folder.