Do one at a time. Only the block size change needs reformatting, the other changes are non-destructive. The MaxTransfer change should already cure the problem. The buffers change should be done anyway, because it increases speed and stability (but also memory consumption).
When talking about formatting, quick is sufficient, you don't need a full format. So it shouldn't take such a long time. I just wanted to warn that all files are lost, so you should make a backup before this last change (or be prepared to reinstall).
Doubling the block size will increase the speed again, but it also increases wasted disk space and it dramatically increases memory consumption by buffers. (Memory needed is number of buffers * block size.)
Bye,
Thomas
