Fooling ReadyBoost
ReadyBoost is intriguing and I've been wanting to play with it since I first installed Vista, but my 1 gig USB memory stick tests as too slow, so ReadyBoost refuses to use it.
While reading part 2 of Mark Russinovich's excellent series on the Vista kernel, I came across his 
screenshot of the EMDMgmt registry key, which is where ReadyBoost caches the specifications of your memory device.
There were a few entries in here and I didn't know which corresponded to which device so I deleted them all, and inserted the memory stick. ReadyBoost again tested it and deemed it too slow. I removed it, and looked in the EMDMgmt key again and presto, there was one entry.
After updating this entry so the values matched those in the screenshot, I reinserted the key, brought up the properties for the USB drive, and it showed ReadyBoost was available!
Now, the theory is that in my case, ReadyBoost will actually make my system slower, since the RAM or the transfer rate for my USB stick is slower than the hard disk - there's not much point in caching if it takes longer to get the cached data than it does to get it from disk - but that's not the point. Now I get to play with ReadyBoost.