Update README

README

@@ -20,8 +20,11 @@ lab6: scheduling
 lab7: mutex/sync
 lab8: filesystem
 
-If you don't want to install ubuntu and other softs to finish these labs in Windows, you can use VirtualBox soft (https://www.virtualbox.org/) and
-a virtual disk image with all these softs. Below example is shown how to setup lab environment in Windows.
+WORK IN MS WINDOWS
+------------------
+Working in Linux is encouraged. But If you Like to work in MS Windows, we provide virtual machine environment (Runnint Ubuntu in VirtualBox) in
+Windows to help you to finish the labs. If you don't want to install ubuntu and other softs to finish these labs in Windows, you can use 
+VirtualBox soft (https://www.virtualbox.org/) and a virtual disk image with all these softs. Below example is shown how to setup lab environment in Windows.
 You can download this virtual disk image -- oslabs_for_student_2012.zip (576.2MB,) from  http://pan.baidu.com/share/link?shareid=69868&uk=2585194235, which
 is an VirtualBox disk image (contains ubuntu 12.04 and needed softs, and is zipped with zip and xz format), and can be unzipped 
 by haozip software (http://www.haozip.com).