- How do you mean "downloading"?
- A rar file is file with .rar extension, a .dmp file is a file with .dmp extension. It can't be both at the same time?
- What are the names of the files, what the contents and in what folder are they created?

- Can you uninstall iStart from control panel?
- Can you disable iStart in your browser?
- What browser?
- Does iStart disappear if you reset the browser to it's initial state?

- Does System Restore back to before last night solve everything?

- If Vipre doesn't find anything, did you already try other tools, like the ones given by Grif in

- What files did you download just before this began?