What's so great about having a processor that has a SSE-2 instruction set? FWIW, SSE2 was first introduced on the Intel Pentium 4. That will teach us - buy Intel.
"I can understand that a video game or a multimedia application needs SSE2/SSE3 support to increase its performances, but I believe an antivirus should not if it breaks the compatibility with old (yet still in use) devices."
Thanks tonyl and bob3160 for the download locations of the outdated Avast 2015 10.4.2233 program. I found it here
http://www.afterdawn.com/software/security/antivirus/avast_free.cfm/2015__10_4_2233_, as well. I'm considering switching to the Panda Free Antivirus program that I don't believe requires the multimedia SSE2 CPU instruction set on this "old workhorse" PC, formerly my main system.
Besides; an up-to-date Avast program with current antivirus definitions several years ago (on 10-2-2013, to be precise), allowed the Zeroaccess Rootkit to partially install on this PC. I believe Avast was responsible to limit the rootkit to a partial install of this variant of the Zeroaccess Rootkit. This PC, now, when first booted into Windows 7 has 100 percent CPU use for approximately one hour. The other symptom of this variant of the Zeroaccess Rootkit is the following, as reported by the program Rkill:
ALERT: ZEROACCESS rootkit symptoms found!
* C:\Program Files\Google\Desktop\Install\{ab64b0fd-f6db-18fd-b31c-59c71c65bda3}\ [ZA Dir]
* C:\Program Files\Google\Desktop\Install\{ab64b0fd-f6db-18fd-b31c-59c71c65bda3}\ \ [ZA Dir]
* C:\Program Files\Google\Desktop\Install\{ab64b0fd-f6db-18fd-b31c-59c71c65bda3}\ \...\ [ZA Dir]
* C:\Program Files\Google\Desktop\Install\{ab64b0fd-f6db-18fd-b31c-59c71c65bda3}\ \...\ﯹ๛\ [ZA Dir]
* C:\Program Files\Google\Desktop\Install\{ab64b0fd-f6db-18fd-b31c-59c71c65bda3}\ \...\ﯹ๛\{ab64b0fd-f6db-18fd-b31c-59c71c65bda3}\ [ZA Dir]
* C:\Program Files\Google\Desktop\Install\{ab64b0fd-f6db-18fd-b31c-59c71c65bda3}\ \...\ﯹ๛\{ab64b0fd-f6db-18fd-b31c-59c71c65bda3}\L\ [ZA Dir]
* C:\Program Files\Google\Desktop\Install\{ab64b0fd-f6db-18fd-b31c-59c71c65bda3}\ \...\ﯹ๛\{ab64b0fd-f6db-18fd-b31c-59c71c65bda3}\U\ [ZA Dir]
* ALERT: ZEROACCESS Reparse Point/Junction found!
I have not yet found a way to completely remove this very hard to remove variant of the Zeroaccess Rootkit.
And, just as important, in the last five months I had problems with this PC downloading and installing Windows Updates. I don't believe this Windows Update problem is related to the installed Zeroaccess Rootkit, but may have something to do with Microsoft .NET (specifically, Microsoft .NET Framework 3.0 Service Pack 2) and the failed patch (KB3135988) install from Windows Update in February 2016.
So, thank goodness this PC, now, is behind a DSL router. However, I would really like to get the Zeroaccess Rootkit off this PC. I have removed part of the Zeroaccess Rootkit using Spybot Search and Destroy capability to detect rootkits. But, I believe some manual modifications of the system registry file is required to remove the remainder of the rootkit. And, I have not been able to find anything on the Internet providing specific instructions for these system registry file modifications.
I have also tried numerous other programs (Avast 10.4.2233, rkill 2.8.4.0, TDSSKiller 3.1.0.9, ComboFix 16.4.29.1, RogueKiller 12.2.0.0, Symantec's FixZeroAccess 1.0.1.7, Junkware Removal Tool 8.0.6.0, Spybot Search and Destroy 2.4, RootRepeal 1.3.5.0, and [Malwarebytes Anti-Malware 2.2.1.1043 - that won't install BTW, probably due to non SSE2 instruction set CPU]) to remove the rootkit, to no avail.
And, of course, I would like to fix the the Windows Update problem. The "Extended support" -- the period during which Microsoft continues to provide for free security updates for products -- doesn't end until January 14, 2020 for Windows 7 SP1.