[Technology columnist Walter S. Mossberg answers readers' questions]

　　专栏作家莫博士就有关电脑和其他电子设备的常见技术问题答读者问。

　　Q: Some time ago you wrote in an article about software that erases files and then records over them, as the safest way to clean off a hard disk. Could you please identify the software?

　　问：一段时间以前，你在一篇文章里写道，有种软件可以擦除文件并写入新的文件予以覆盖，称它是最安全的硬盘清理方式。能不能说说到底是哪款软件？

　　A: If you are using a Windows PC, there are multiple programs, both free and paid, called 'file wipers,' that can do this. One I have recommended is Window Washer from Webroot, which, among other things, does what the company calls 'bleaching' of files so they can't be easily recovered. If you're using a Mac, a similar feature is built right into the latest operating system versions. It's called 'Secure Empty Trash' and is found in the Finder, the Mac's equivalent of Windows Explorer.

　　答：如果你用的是Windows电脑，那么有多种程序可以做这件事情，有免费的也有付费的，都叫“file wiper”（文件擦除器）。我曾经推荐过的一款软件是Webroot公司推出的“Window Washer”，按这家公司的说法，它可以对文件进行“漂白”，这样文件就不能轻易恢复。如果你用的是Mac电脑，最新版操作系统其实已经内嵌了一种类似的功能。它名叫“Secure Empty Trash”（安全清倒废纸篓），在Finder（相当于Mac的Windows Explorer）里面。

　　Q: In your recent article about transferring Internet video to your TV, you ignored Apple TV. Why?

　　问：你最近关于把网络视频转到电视上的文章中没有提到Apple TV，这是为什么？

　　A: Because the article was about methods for wirelessly streaming video from multiple Web sites via a PC to a TV, and that's not what Apple TV primarily does. It mainly takes audio, video and photos that are already on your computers and plays or displays them on your TV. It only directly streams in real time from YouTube and Internet radio sites, plus content being downloaded from iTunes. Unlike the two products I covered, Apple TV doesn't allow you to stream movies or TV programs from a variety of Web sites you choose, like Hulu or CBS.com.

　　答：因为那篇文章是关于用什么样的方法将多个网站的视频从电脑无线导入电视，这跟Apple TV的主要功能不一样。Apple TV主要是提取电脑上已经有的音频、视频或图片，然后在电视上播放或显示。它只能实时播放YouTube和一些网络电台网站上的内容、还有通过iTunes下载的内容。和我以前提到的两款产品不一样，Apple TV不允许你从你自己选择的多家网站导入电影或电视节目，如Hulu或CBS.com。

　　Walter S. Mossberg