The thought of a portable Visual Basic, while impressive, would represent a significant threat to Java, and would challenge its supremecy over its most important feature - portability. For more information, visit the commentary at the Java Lobby site. However, users that choose a custom install, or use a typical install, will still have access to Java. Users are free to download the virtual machine from Microsoft. However, developers also have the flexibility to avoid Microsoft's JVM entirely, by choosing to use Sun's Java Plug-in.
Applets execute under the control of a web browser.
Netscape and Internet Explorer impose a security restriction, that prohibits access to the local filesystem by applets. While this may cause frustration for developers, this is an important security feature for the end-user. Without it, applets would be free to modify the contents of a user's hard-drive, or to read its contents and send this information back over a network. Digitally signed applets can request permission to access the local filesystem, but the easiest way around the problem is to read and write to remote files located on a network drive. For example, in conjunction with a CGI script or servlet, you could send HTTP requests to store and retrieve data.