The Problem. Reduced ability to accomodate memory - seems to be the number of GB rather than number of sticks but could be the number of full slots. Sympton is boot failure fixed by removing memory sticks. How it developed Had boot problems. Over a period of months it took 2 -3 rebooots, then 10 then 20 then infinity. Had 4x512MB installed. Solved problem first time by removing 1 512Mb RAM stick. Ran OK for a while with 3x512 then same problem again solved by removing another 512mb stick. Was working OK but 1G not enough and as there seemed to be damage on the gold contacts I bought 2x1GB thinking the RAM sticks were the problem and I could insert the 2x1GB to get total of 3GB. Didn't happen. Removed 1 of the two 512mb located side by side - now would not boot first time even though I had removed not added. Tried various combinations of 512mb and 1GB sticks and found that there seemed to be no one stick or no one slot that was identifiable as a problem. The board will accept 2x512mb or 1x1GB but not 2x 1GB which is the minimum I really need. Did not try 512mb + 1GB. Usually it got as far as mouse and keyboard lights before stalling (stalls before monitor backlight come on) before I removed the offending sticks. Now it gets this far with 2x1GB and then stalls before monitor backlight, but does NOT get this far with all slots full i.e 2x1GB and 2x512mb. boot hangs earlier it seems. Observations that may help someone to isolate the problem: Boot problem was not present with warm start ie. green restart button pressed unless I set CHKDSK in which I had the non boot problem. If during a power cut I kept the UPS on with PC switched off it would usually (but not infallibly) boot first time. If I switched off UPS there was always a problem rebooting and usually also a problem with Samsung monitors claiming they were not connected to PC. Had problems with a previous quad card not running all four monitors after a switch off. Have tried without UPS and it makes no difference so not UPS. Already tried a new Power Supply. Suggestions: I think this is some kind of dying mainboard/component problem - which means it is going to be hard to isolate/fix - but could it be something simple like bad earthing? The problem is linked to mainboard power off rather than PC power off it seems. As I understand it there is power flowing to the main board when PC is switched off. I think I have eliminated total memory+ total page file being over the (4GB?) limit as a possible cause but not entirely. Any suggestions?