Can’t download file most of the time and web browers terminate loading some

These two issue may be related. I can’t consistantly download files. I usually get msg:”c:\….temp\..file name can’t be saved. Source file can’t be read” Yet i can click on a file or program Update and it downloads just fine.When I use any web browser some web site links and some web some menu selections will cause the browser to shut down. I believe I’e removed all viruses, all spyware, all malware from XP and from safe mode. I think there are one or more files that need to be re-registered. Which ones and how? Re-running windows XP did not repair any thing, I do not want to re-load windows. I believe I posted this question before but I can’t find it in any forum, nor has any one responded. Maybe I’m not using the forum properly?