Close outlook and go to documents and settings\username\local settings\microsoft\outlook and cut the two files in there. Now paste them on the other drive where you want them.
Open outlook and it will scream at you saying the pst file is missing. Point it to where you pasted it. It will scream again saying something about folders, say NO and outlook will bomb out.
Start outlook up again and all should be fine.
Copy the two files mentioned above (copy not cut) and put them where you want them.
Open outlook as normal and select file/data management. Tell it here where your files are. now close outlook and remove the original two files.