I have Monaco font. The Ubuntu says that it is monospaced, but Windows XP doesn't. Is there anyway to tell Windows that it is monospaced(e.g. change some options with help of FontForge or whatever)
From the FontForge FAQ:
How do I mark a font as monospaced? You don't. Just ensure that all the glyphs in the font have the same width and then FontForge will automatically mark it as monospaced for you. (If you mark it as monospaced incorrectly some rasterizers will give strange results). If you want to set a font's panose values yourself (Element → Font Info → OS/2 → Panose) then set the Proportion field to Monospaced. This is necessary but not sufficient to mark the font as a whole as monospaced. If you are unsure whether all the glyphs in your font have the same advance width use Element → Find Problems → Random → Check Advance.
This seems to work, so check it with your font file.