I thought for once I could get a new IBM 5150 and NOT have to come crawling to the group for advice, but noooo.. Just got an ebay 5150. I couldn't resist - it was relatively local, and included a 5151 monitor (but no keyboard), for a decent price. I have a keyboard, so no worries. Took the top off to peek inside to confirm everything was seated, etc. I started it (with the top off) and got a keyboard error (301). I discovered that my keyboard was set on AT instead of XT. Flipped that switch and viola, the 5150 booted with a Dos 2.11 disk. Poked around the disk, ran a Basic file that happened to be on it, tested the "B" drive, formatted a disk - it's all good. I even booted a few times with no issue. I put the lid back on and started it again. This time I get this. 40FF . and the PC is beeping away, long beeps that do not stop! I restart again and get this. 40FF 201 301 This time there's no beeping, it just displays the msg. The disk drive was read from briefly, then nothing. I pull out what appears to be a memory expansion card. Here <https://dl.dropboxusercontent.com/u/65762317/forums/IBM_5150_RAM_board.jpg> 's a picture of it. I started it without the card and get this. 40D0 I took another look at that RAM card and found THIS on the back <https://dl.dropboxusercontent.com/u/65762317/forums/5150_bug.jpg> ! My PC had a bug. Anyway, cleaning that up didn't help. I replaced the card, started it and got yet another, different 40xx error. OK, where do I go from here? The darn thing worked at one point today; why not all the time? I have looked for unseated chips, cards and cables, as least as far as I could without pulling a floppy drive, and found that everything is secure. Thanks as always, Steve