日本語PowerPoint (2002)で半角円マークの代わりに半角バックスラッシュを使う方法
Use backslash (instead of hankaku-yen) in Japanese version of PowerPoint (2002)

(結論: 「Microsoft Office ツール->Microsoft Office XP 言語設定」で「既定のMicrosoft Officeバージョン」を「英語(U.S.)」に変更)
(In short: in "Microsoft Office tool->Microsoft Office XP language setting", set "default Microsoft Office version" to "English (U.S.)")

I use PowerPoint to make figures for papers. When I need to put some math formula, I used to use the equation editor came with MS Office. However, its user interface is not so great and equations are not very beautiful. I wanted to put equations just as I do in LaTeX.

There are some software for that. TexPoint is famous, but it is a shareware. I tried some of similar software and came to the conclusion that TeX4PPT is the best.

I was using TeX4PPT for a while without any problem. Then one day, I noticed that I cannot write "\cap": every time I try, division symbol ("\div" in LaTeX) appears. I also found that the same problem is happening in the ppt file that came with TeX4PPT. I had no clue at first, but I noticed the character code of "\cap" is 0x5c (in cmsy10), which is backslash in ordinary fonts. Then I found there are a lot of issues around backslash and hankaku-yen symbols, which are used interchangeably in Japan.

Basically, we cannot input backslash in Japanese version of PowerPoint, because it automatically converts backslash to hankaku-yen, as described in the following page at MS:

http://office.microsoft.com/en-us/ork2003/HA011402151033.aspx
Converts the backslash character to a Yen symbol when the installation language is Japanese.
There are multiple people asking about the same problem (such as this, this, and this (all in Japanese)) and none of them gave me the solution. There is also an article on experts-exchange.com, which you need to pay for viewing. I signed up for it (using 7 day free trial) to take a look at it, but their solution did not work for me.

Then I changed the language setting (as written in the beginning) and it just worked. Now a backslash appears as a backslash. I cannot write hankaku-yen now, but I'll never use it anyway. TeX4PPT works as well, though I needed to reinstall it.

Update on 2010/05/21
It's getting weird on TeX4PPT again. I can put any characters, but these are garbled after I save and reopen the document. This is quite annoying. Considering PPTs made with TeX4PPT are not portable, maybe I should find some other ways.
Update on 2010/08/04
For presentation purpose, I ended up using TeXclip. TeXclip is a browser-based equation editor that allows you to copy and paste the image of equation and also to download it as an eps file. It's very easy to use and I love it.
For making figures for papers, I'm using inkscape with textext, after I started using Ubuntu for my desktop PC. Inkscape is a great drawing software that allows several tricks that powerpoint cannot do and textext is an add-on for embedding latex equations. One problem for me is that I cannot use the shortcut keys for powerpoint.
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