I assume this is happening during power down (like sleep or hibernate) or recovering from it? Either way, it appears sptd.sys is causing this. It is not properly unloading itself, which usually happens during a power down. This driver is responsible for supplying the advanced virtual drives for Daemon Tools, and it has been known to commonly cause bugs. While usually one would recommend you remove it, I do notice that this one is very, very old (Jun 2006). You'll most certainly want to update Daemon Tools as well as the the accompanying SPTD driver. If it still is causing you woes, you're going to have to write it off as a buggy driver and forgo using SPTD. Note that Daemon Tools only needs SPTD for advanced security emulation like SecuROM. It does not need it for normal drive emulation.