Luso,
MSVCI70 is one of 3 files which Avast will overwrite during an update.
The others are MSVCR70 and MSVCP70.
All 3 are runtime library files which you should be able to download from Microsoft.
Do a computer Search to ascertain if the others are loaded.
If you can't find the file, let me know and I will see if I can get a copy to you.
The links Shgoh provided should be very helpful.
Techie