I have seen this problem on several brands of PCs where a hard boot will hang the machine on reboot. Alienware seems worse than others. On others you just power down via the switch wait 15 seconds & power on again.
On Alienware you must discharge the ROM memory by unplugging from AC, pressing the on/off button to a count of 20 re-connect and THEN turn the switch on. I've seen this with XP pro, Vista & Win 7 on HPs, ACER and Dell and SONY I have not even called Alienware on this cause they're gonna give me some line of bull that will not fix the problem. In other cases I've tracked the problem to an OS/ BIOS issue which neither Microsoft or the hardware Mfg will admit to but I am inclined to believe it is an OS finding an unstable system after the cold boot. I am however astonished as to the production quality of Alienware . I am returning my second Aurora R4 today and it seems I am not the only one. Certainly the Alienware products do not have the rock solid quality of the DELL line or their design is so complicated (way too many pretty lights) that the BIOS has problems keeping what REALLY needs to work stable. But that is MY opinion.