Actually, I just had this, but it was even more temperamental. I had to hold down my left button and then scroll with my wheel. I'm using a Kensignton Mouse, but that shouldn't really change behaviour like that. At least, I've never known anything else to misinterpret it so. All to say, you may need to do some weird stuff in this window. (BEWARE OF IMPENDING SOAPBOX...here it comes...) As others have said, I find Disk Allocation relentlessly frustrating. If I use an existing session as a basis for a new session on a different hard drive, why oh why does it make the session folder on the new drive but leave the Disk Allocation (the Audio Files folder) to the old drive? Why doesn't it default to updating it? Or at least have us be able to choose it as a preference? I've wasted so many hours of the past nineteen ProTools years on this counter-intuitve default. And, while on the subject, why, if I redirect the location once in Disk Allocation, can it not remember that location the next time I open the Disk Allocation location selection? Wish that stuck.