At starting windows Alert ! unsupported memory configuration please p;pulate DIMM1 (desktop dell optiplex gx 755)

If the computer was working well and this error popped up, then the most likely issue is a bad memory module, most likely in the DIMM1 slot. If this occurred as a result of a new build or an upgrade, then there are other possibilities. Mainboards are particular in many cases where memory modules can be installed and in what groupings/types/speeds can be mixed and matched. The problem could be as simple as removing and re-seating the memory module in the DIMM1 slot (the slots are usually marked on the mainboard). If there are multiple memory cards installed, try rearranging them, or even removing all but one at a time to try to determine if there are any bad ones. If you are using one at a time, they usually have to be installed in the DIMM1 slot (but not all mainboards require this). After you determine if there is bad memory and which one is bad, you can either replace the bad module, or operate the unit with the remaining good modules, although performance may suffer slightly. The last possibility, and the worst one, is that the the DIMM1 slot on the mainboard is bad. If that is the case, and if you cannot operate without a DIMM in slot 1, you will need a new mainboard or new PC.

these can be related as the main battery on the motherboard is need to retain cmos setting when a system is unplugged from a/c power for extended periods of time.
so the loss of cmos would prompt you about certain components including amount of memory(pending no changes in memory amount/ slot location as a single chip unit must have the mem in slot 1). there is a round 3.0 volt battery that once reports bad, should be replaced. start there and see if you get any other errors. as there could be a problem with the powersupply or motherboard if that doesn't resolve it.

There should be 4 DIMM slots - two with white tabs and two with black tabs. DIMM 1 should be the white tabbed slot closest to the processor. Slots 1 and 3 (both white tabbed slots) should have RAM installed first, then slots 3 and 4 for additional RAM. If Slot 1 already has RAM in it, pull it out and push it back in to reseat it. If that doesn't work, replace the RAM in Slot 1.

are u trying to start windows with a fresh copy install only

try to open your cpu set then clean the pins of the memory as well as the memory slot, their is a possible that dust could cause the problem.

System will not boot without RAM in Memory slot 1
http://support.dell.com/support/edocs/systems/op755/en/UG/HTML/memory.htm
If you have memory in that slot, then remove and re-seat it per the instructions in that link

in computers there are many kind of rams a big problems of ram which users are always face is buss speed different. we cant run all type of bus speeds of ram on our computer please replace your ram with the higer bus speed and run it.


and pull out your one ram from your ram bank. i mean to say decrease your ram speed.

Dell Optiplex 755 supports a maximum of 8GB of memory. Memory modules should be installed in pairs of matched memory size, speed, and technology. If the memory modules are not installed
in matched pairs, the computer will continue to operate, but with a slight reduction in performance.
DDR2 Synch DRAM Non-ECC Memory 667MHz or 800MHz speeds are supported.
For further details please refer to Product Technical Specs (Page 12)

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CreativeTECH

open it up ..and see what is wrong with the first slot of ram memory ...if the inserted module is not working ...than remove it ..(to check if it works just leave it by itself and try to start the computer ..) anyway ..if there isn't any module in the first slot ..than move one from the last slot ..I mean mount the modules in slots from number 1 to ...as many you have available ...After finish ...restart ..press delete button right the way to go to bios settings ...and in here ..look for optimal factory default settings ..and engage them by selecting with arrows..and enter..and confirm with enter (Y)
to save settings before exit ..press F 10 ..and enter ..
This will assure the ram configuration ...in the correct way ..
Please read careful ..and ask if you do not understand something ...and also ..please rate my answer..cause it helps with my rating and activity on the site..

Hi, You can try power drain first. Power off system , disconnect power and press and hold power button to discharge stored power, then remove memory module 1, then reseat it by inserting it with the levers extended to the sides and press down with thumbs until the levers snap in place vertically on their own. if no change, replace module. \quote While reseating the Memory Module please Handle with care. Quote/