I have XP home and yesterday had a crash, well not so much a crash as it started to go mega-slow so I turned it off. I ran virus scans and spyware scans etc when I started back up and all was fine. The only problem is since this happened all the symbols in windows such as - the symbol in a pull down box, - the little tringle to expand folders in the start menu, - bullet points and numerous other things seen in programs and web pages have all been replaced with a very small unrecognisable 'squiggle'

. It seems Windows has lost some file or font somewhere but I have spent ages trying and can't find out what is wrong. Does anyone know what might be the problem and what I could try?
Many thanks in advance
Steve