Ok, let's see if I have this straight.

You have 3 disks in a raid 5 config. The one resultant raid array is then divided into 3 partitions, c:, d: and e:

Is that correct?

If so, you still need more disks. You have the OS, the swap file, tempDB and the user database and log sharing the same physical drives. That's not recommended, to put it mildly.

Optimal solution:

Move the OS and the windows swap file off the RAID 5 array. At best the OS needs raid 1. You can get away with a single disk if you're short of cash and willing to take the risk.

TempDB should be on its own physical drive. Not sharing physical disk with anything else. You can probably get away with a single disk here as TempDB is recreated every time SQL starts, though Raid 1 is better for redundency. Depends what the uptime requirements are for the system.

If you can, convery the 3 partitions on the RAID 5 into 2 partitions and leave the data file on there and the backup in the other partition.

The log should be on separate physical disks from the data file. RAID 1 is best here. RAID 5's a bad idea for log files

If you can't afford the disks for the optimal solution, at minimum get 2 extra drives. One for the windows swap file, one for TempDB