RE: DELL POWEREDGE 2850 RAID 5 with 4 Disks, 1 Disk Failed and 1 Disk Predictive failure. Not starting.
RAID 5 can only recover from a single drive failure. If the data is important and you don't have a valid tested backup then you should contact a data recovery company.
If you want to attempt to recover the array it may be possible to force a drive online or import a foreign configuration, depending on which controller you are using. Before you attempt any recovery on the array you will want to remove the new drive you just inserted to avoid it being brought online in the array. You will want to have the last drive that failed and brought the virtual disk offline in the system.