How can I make Windows 7 ReadyBoost persistent?
After messing with various parts of the registry (failing to achieve anything significant there) and being unwilling to do a fresh OEM style scripted install of my system I have found a way to do something sort of similar to what I wanted to do.
Unfortunately - what I did is not free. I opted to use a third party program called eBoostr (version 4, desktop edition). It is intended for windows XP originally and does basically the same stuff what ReadyBoost does. However, it works fine in Vista and Windows 7 as well. It can use up to 4 cache devices (including hard disks, but it's not vewry effective with hard disks) and keeps the cache over the reboots by default. Using encryption on removable disks is optional.
So I am using eBoostr on internal CF card in IDE slot and letting superfetch / ReadyBoost handle the prefetching into RAM part and few USB sticks.
Readyboost/Superfetch and eBoostr seem to work fine together as long as you point them at different drives (using the same USB stick for both ReadyBoost and eBoostr is not very effective).
The program cost is around 25 - 30 $ (and there is free trial available with full functionality) but I found some online shop in UK that was selling the desktop edition for 12.9£ and shaved 5£ off the price when I ticked a chekbox allowing them to send me spam. So the end cost ended up being around 9 euros for the desktop edition (that does all I need as superfetch is already capable of using RAM for cache).