When formatting a disk in windows the default blocksize is 4K. You must choose a different blocksize (64K) and format the disk for best performance for SQL. A format will loose anything on the disk so you need to move all of your folders/files from the disk to another disk, format the disk then move the folders/files back. Also, if you just move the files and create new folders after reformatting the drive you will have to add permissions to the folders to get SQL to start.

Here is the process assuming that you have a drive named G: where tempdb is located:

1. Stop SQL

2. Move the folders/files from G: to another disk

3. Format G: and specify 64K as the blocksize

4. Move the files back to G:

5. Start SQL

For TempDB you want multiple DATA files. You only need one TempDB LOG file.

Hope this helps!