If you only want to change the location of the uploads directory (and leave the rest of WordPress on C:), you should be able to define the UPLOADS constant:

define( 'UPLOADS', wp_normalize_path( 'e:\path\to\uploads' ) );

I’d recommend you do this on a test machine first, if at all possible. I’d also recommend you do this in a plugin somewhere — possibly a Must-Use plugin.

Caveat: If you’ve already got files uploaded, you will probably need to move them manually to the new location. (I’m not sure if, but I suspect that, WordPress will find them there, as long as you maintain the same file names.)

Reference

• wp_upload_dir() » Folder Name
• wp_normalize_path() (to convert Windows paths for use by PHP)
• Writing a Plugin
• Must-Use Plugins