I tried searching on "MUTEX" but could not find much. I'm trying to assist a friend with his wife's Dell Deminsion 4700 running XP Media Ctr w/ SP3. He got the following msg. "kernel thread terminated while holding a mutex" Now the PC hangs at Windows start up. We can get it to boot in safe mode (build 2600.xpsp_sp3_gdr.100216-1514:service pack 3). The PC didn't come with an OS disc. If we have to reinstall (don't want to do this) we must use the Dell PC Restore on the D: drive. Can someone tell me what to do? We tried a system restore to an earlier working date but had no success. Thanks for reading this. UPDATE: I turned off system restore and got the following error... "instruction at 0x7c9101b3 referenced memory 0x004a195acound not be written". I hope this helps.