=== Details ===
If you have Windows XP with the SP2 update, you already have a working system. The Kartika font which comes with the SP2 update is a decent font. But you need to install any Unicode 5.1 compliant fonts to see new chillus.
The most likely reason why you cannot see anything on the Malayalam Wikipedia is that you do not have a font that supports the Malayalam Unicode range. If you can see some letters, but there are too many errors, you probably have a font with poor support for Malayalam Unicode. Perhaps the best fonts available are [http://www.chintha.com/fonts/rachana.exe rachana] by K.H.Hussain [http://varamozhi.sourceforge.net/fonts/AnjaliOldLipi.ttf Anjali Oldlipi] by [[ഉപയോക്താവ്:Kevinsooryan|kevin]] [http://www.supersoftweb.com/Download/TholiTrd.TTF ThoolikaTraditional Unicode font]. They work almost perfectly in Windows 95/98, ME, 2000, and XP (especially with Internet Explorer 5 or over). Please download the fonts by following the above links and install them. To install, copy the fonts, open "Fonts" from Control Panel and paste the fonts in the Fonts directory.