New 256 Mb RAM in Compaq Presario 17XL2 not...

Question

Bought two 256 Mb sticks to replace the one 64 Mb that came in the laptop Presario. PC won't even put logo on screen so apparently no POST. Replacing the outboard card with the original (leaving the new card in the inboard slot) shows a POST summary with 320Mb and boots to a message that ''himem.sys has detected unreliable XMS memory at 04001960...'' . Opened the configuration tool and found 64Mb maximum - increased to 512 with no improvement. Machine will boot with 64 Mb card in inboard slot unless new card is in outboard slot then no POST. Found one internet post that there might be an ECC/non-ECC issue but no option on CMOS setup. The new chips read 256MB synch 133MHz CL2 and PC133-333-542 plus MT1BLSD8464G-13381. I have replaced the Pentium with a Celeron if that matters. Thanks for any assistance whatsoever.Don