• The costs of redesigning the system are prohibitive because it is large, monolithic, and/or complex.
• The system requires close to 100% availability, so it cannot be taken out of service, and the cost of designing a new system with a similar availability level is high.
• The way the system works is not well understood. Such a situation can occur when the designers of the system have left the organization, and the system has either not been fully documented or such documentation has been lost.
• The user expects that the system can easily be replaced when this becomes necessary.
• The system works satisfactorily, and the owner sees no reason for changing it; or in other words, re-learning a new system would have a prohibitive attendant cost in lost time and money.

If legacy software runs on only antiquated hardware, the cost of maintaining the system may eventually outweigh the cost of replacing both the software and hardware unless some form of emulation or backward compatibility allows the software to run on new hardware. However, many of these systems do still meet the basic needs of the organization. The systems to handle customers' accounts in banks are one example. Therefore the organization cannot afford to stop them and yet some cannot afford to update them.

But now that Legacy is clear developed we release a first compilation of XOOPServer buitl on Apache 1, MySQL 4 and PHP 4

http://code.google.com/p/xoopserver/downloads/list