|All drive letter assignments in the operating system are for logical drives. |
When you remove a logical drive that is designated removable, it isn't necessarily assigned the same drive letter the next time it's detected by the operating system.
E.g. When you removed (STOPped) the E drive, when the same drive partition is detected again, e.g. after a reboot, if there were other drive letters available lower than E while booting, then that drive partition will be assigned a drive letter other than E. The operating system will assign the lowest available drive letter, alphabetically.
Whatever hard drive partition that was formally assigned E should show up fine in Disk Management, if there's nothing wrong with it's hard drive's data cable connection or power connection, but it may no longer be assigned E.
If you want to change the drive letter assigned to it, you can change it in Disk Management to any available drive letter, except that you can't change the drive letter for the hard drive partition Windows was booted from.
(e.g. Control Panel - Classic view - Administrative Tools - Computer Management - Disk Management.)
If the drive letter you want to assign isn't available, you can change the drive letters assigned to other things to free up the drive letter you want to use.
The drive letter assignment will stay the same for sure as long as you don't accidently remove the logical drive it was assigned to again, or in the case of USB or firewire connected drives, until you have unplugged the physical drive and then have started up the operating system at least once with it unplugged, in which case the logical drive MIGHT be assigned a different drive letter than it was previously, when it's detected again.
Apparently, if your mboard has one of certain main chipsets, e.g. nVidia nForce 4 , SATA internal drive partitions are seen by the operating system as removable drives.
However, sometimes that's not the case, and the hard drive was un-intentionally designated as a removable device, in which case a drive partition, or drive partitions, on it is (are) seen as (a) removable logical drive(s).
Go to Device Manager - Disk Drives - RIGHT click on the model of the hard drive that the partition formerly known as E was on - if Optimize for quick removal is selected, try changing that to Optimize for performance, reboot, look there again to see if that selection has "stuck" . If it has, select Enable write caching on the disk, if you can, however, if you do, don't remove the logical drive, or you may lose data.