Legacy System Still Going Strong

Hello All,

I currently have a legacy system that is around 8 years old. The system is an essential system that runs on a mission critical custom made software built for purpose.

The system comprises of:
1x Dell Server 2850 on RAID5
6x Dell OptiPlex 280 Desktops

My problem is these systems are now becoming old, we have just replaced the memory in the Server, and recovered from a failed HDD. These systems run 24/7 and have performed admirably over there time.

I would like to try and think of a recovery plan if one of these system fails, I would like to implement Virtualisation however this is not supported by the third party vendor. If a HDD failed on a desktop I would have no way to recover the data.

To replace the system will cost £85,000 so ideally I would like the recovery program to last the sands of time.

I was wondering if anyone could think of a valid alternative to my predicament.