It's OK to use the abbreviation “PC” to refer to a certain kind of computer hardware, but please don't use it with the implication that the computer is running Microsoft Windows. If you install GNU/Linux on the same computer, it is still a PC.
The term “WC” has been suggested for a computer running Windows.
Please avoid using the term “photoshop” as a verb, meaning any kind of photo manipulation or image editing in general. Photoshop is just the name of one particular image editing program, which should be avoided since it is proprietary. There are plenty of free alternatives, such as GIMP.
Please avoid using the term “PowerPoint” to mean any kind of slide presentation. “PowerPoint” is just the name of one particular proprietary program to make presentations, and there are plenty of free alternatives, such as TeX's beamer class and OpenOffice.org's Impress.
In the late 1990s it became feasible to make portable, solid-state digital audio players. Most support the patented MP3 codec, but not all. Some support the patent-free audio codecs Ogg Vorbis and FLAC, and may not even support MP3-encoded files at all, precisely to avoid these patents. To call such players “MP3 players” is not only confusing, it also puts MP3 in an undeserved position of privilege which encourages people to continue using that vulnerable format. We suggest the terms “digital audio player,” or simply “audio player” if context permits.
Linux is the name of the kernel that Linus Torvalds developed starting in 1991. The operating system in which Linux is used is basically GNU with Linux added. To call the whole system “Linux” is both unfair and confusing. Please call the complete system GNU/Linux, both to give the GNU Project credit and to distinguish the whole system from the kernel alone.
A hacker is someone who enjoys playful cleverness—not necessarily with computers. The programmers in the old MIT free software community of the 60s and 70s referred to themselves as hackers. Around 1980, journalists who discovered the hacker community mistakenly took the term to mean “security breaker.”
Please don't spread this mistake. People who break security are “crackers.”
“LAMP” stands for “Linux, Apache, MySQL and PHP”—a common combination of software to use on a web server, except that “Linux” in this context really refers to the GNU/Linux system. So instead of “LAMP” it should be “GLAMP”: “GNU, Linux, Apache, MySQL and PHP.”