windows 7 - Whenever I open a program, Internet Explorer opens and tries to download it

My Asus laptop had some viruses. I scanned it and deleted 12 viruses but I am still getting problems when starting programs.

I tried to open Paint, Task Manager, Regedit, Chrome, etc. but none of them are working.

When I want to open them, Internet Explorer will try to download them instead of letting me open them.

What should I do?

I think this is the problem with file associations. Your executable files are not behaving normal and they are opened with some other program like Internet Explorer due to some misconfigruations. The Icons of Executable may also not appear as expected. To fix this problem you can follow these steps:

1. Open Notepad and Paste following lines and save it fix.reg or whatever name you like

   Windows Registry Editor Version 5.00
   
   [-HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.exe]
   
   [HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.exe]
   
   [HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.exe\OpenWithList]
   
   [HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.exe\OpenWithProgids]
   "exefile"=hex(0):
   

2. Merge these registry changes to System Registry and restart your computer. After restart your programs should behave normally.

For more details you can refer here

Hope this fixes your problem. Let me know if this helps. :)

EDIT 1 As OP was unable to open any executable including registry editor and command prompt following method can be used to edit registry without booting into windows

1. Download Hiren's Boot CD and Burn the Image on CD or USB Media
2. Boot from the Disc, choose Mini Window XP from Menu. When mini XP is loaded Click Icon in tray and select Registry > Registry Editor PE
3. Set the remote windows directory and make required changes.

Other methods are also available. One is mentioned here Editing a windows XP installation's registry without being able to log in

You should never trust a compromised machine nor attempt to "recover" it using antivirus software.

Read How do I deal with a compromised server? on ServerFault - it talks about servers but pretty much all of it is also true for desktop computers.

Basically, it all boils down to one thing : reinstall the system.

Some people will tell you how to remove that particular virus and bring back your system to life but you'll never be sure if the system is truly "clean" or if there's still some piece of malware (rootkit ?) that's left and that can still do damage in the future or silently spy on you without you ever noticing (and once you'll notice it'll already be too late and your bank account will be empty).

The only way to be certain that you've got control of the system is to rebuild the system. While there's a lot of value in finding and fixing the exploit used to break into the system, you can't be sure about what else has been done to the system once the intruders gained control (indeed, its not unheard of for hackers that recruit systems into a botnet to patch the exploits they used themselves, to safeguard "their" new computer from other hackers, as well as installing their rootkit).