确实存在楼上所说的问题，不过有个帖子是这样说的
http://www.ad.siemens.com.cn/club/bbs/post.aspx?b_id=47&a_id=1116516
要先装STARTER 再装Microwin，自己测试过了，确实是这样。
Question
How can both products be installed on one PC?
Answer
The STARTER setup prevents installing STARTER 4.3.3.0 on a PC with installed STEP7-MICRO/WIN V4.0.9.25. However, it is possible to install STEP7-MICRO/WIN V4.0.9.25 on a PC on which STARTER V4.3.3.0 is already installed.

This means that both products can be installed on one PC:

Uninstall STEP7-MICRO/WIN V4.0.9.25
Install STARTER V4.3.3.0
Install STEP7-MICRO/WIN V4.0.9.25
It is not possible to simultaneously operate the STARTER and STEP7-MICRO/WIN programs.