According to PNY the Gateway 2000 systems compatible with that (new) stick are listed on this page.

With the old stick in slot 1 and the new in slot 2, can you get in to the bios setup screens? If so go in and look around for a setting to "Reset Configuration Data" (which may also refer to ESCD). If you find it, set it to Enabled. Whether you find it or not, then do a Save and Exit from bios setup. See if that changes anything.

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