相信初次使用Keil MDK Version 5的人会发现，以前用Keil4建立的项目打不开了，本经验介绍如何让Keil5可以打开Keil4的项目。
Keil5 MDK Core，MDK v4 Legacy Support
MDK v4 Legacy Support
http://www2.keil.com/mdk5/legacy
MDK Version 5 uses Software Packs to support a microcontroller device and to use middleware. To maintain backward compatibility with MDK Version 4 you may install Legacy Support. This might be necessary for two reasons:
To maintain projects created with MDK Version 4 without migrating to Software Packs.
To use older devices that are not supported by a Device Family Pack.
The legacy pack for MDK v5.25 is the last one. Further MDK releases will not be receive a legacy pack update. This means that there will be no:
Corrections to the legacy device database (UV4.db).
Bug fixes on the RL-ARM middleware or graphics library.
Updates on RTX v4.
Keil5编译器好像不支持中文路径，编译时产生的临时文件暂存在用户变量Tmp中，所以如果你的用户名是中文，编译时就会出错。解决方法是将keil安装在一个英文用户上。
http://az717401.vo.msecnd.net/legacy/MDKCM523.EXE
兼容包的名字是MDKCM523.EXE 针对版本 Keil MDK v5.23