I don't know 'bout u folks, but I have never encountered good experiences w/ Alcohol 120%. Although I installed it to burn .mdf and .mds images, I still have Daemon Tools as my primary Virtual Drive manager. Also, I tried Virtual CD and come to despise the sofware.
The problem with Alcohol 120% for me is that if I mount an image that sits on my harddisk, it will slow my sytem to a halt because it sucks up ALL my ram for a good 5 minutes or so.(I have ram monitor) I thought that's fine since, I won't be mounting images often.... but then cometh the restart or shutdown/bootup sequence.... EVERY bloody bootup, I get a lock up of 10 minutes.... because my ram was sucked away to a red zone of 4mb free! Okay, now I know I can turn off the mount on startup, but what good is a virtual drive when I have to mount it everytime I play since mounting on start up is such a hassel. I tried Alcohol not only once, but 3 times in the past with newer version each time, hoping for an optimized method of auto mounting. No progress on Alcohol's end.
As for Virtual CD, it came in and screwed up my IRQ.... I BARELY reboot from the initial instalation.... then I get the blue screen of death. I'm like, wtf?! I didn't even mount any drives! Blame my system? Don't think so... all my drives are pretty much standard like in any given computer. All are IDEs. I would expect no problem since Virtual Drive utilizes SCSI interface. That was a really horrible experience having to remove it as I was a newbie to computer way back when.
Daemon Tools on the other hand, gives me nothing but good results. It auto mounts the drive from the start and requires much less ram on the mounting procedure. Like all other Virtual Drive utilities, it takes some time to mount the image, but it doesn't make my system into an unusable piece of silicon and plastic...
It only gives 4 drives and not 8 or 16 like other utilities boasts.... "but why?" I ask. I have never simultaneously mounted 4 different images... nor ever do I wish that I'd have the 5th virtual drive as I never get to the 4th. IMHO, the other softwares just have more for boasting rights.... In practical use, 4 is way more than enough.
Currently, I have Prince of Persia: Warrior's Within CD3 mounted(yes I bought it) I mount it because I want to have my HL2 DVD in my only optical drive.(and yes, I purchase all the games I like)
Works like a charm.