If you made it to this thread and you are still using XP and MSE has failed on you(Microsoft ended support for XP on 4/8/14 along with MSE), I have created this thread to help with still-XP users who dont have strong enough computers to upgrade, whether it not be efficient for your machine or whether you just dont feel like going through the work of upgrading it,
The problem is that many of us who use our older but still maintained pc's have XP, but upgrading will cause a lot of work and a change in performance. I still use my 8+ year-old Sony Vaio Laptop as a media device, although now the problem is coming from the lack of Microsoft support, which leads to the bigger problem: lack of support from Micorsoft Security Essentials.
Which leads us also to Ccleaner. If you are a user of Ccleaner(and still have XP) it is a great program but i would highly advice against trying to update at this point as doing so for me caused more virus problems. It may be because I followed a faulty link but I have updated and used Ccleaner(Cookie Cleaner) for years with XP before Microsoft ended suppport and have had no problems.
I would post the specs of my old Sony Vaio at this point but I am currently in boot-scan mode... which lead us to...
I had to uninstall MSE to install Avast! to do a boot scan. WHY?
I am also an avid user of Malwarebyte's Anti-Malware, and I also try to utilize Kaspersky Lab's Rootkit Killer(which did nothing again).
Malwarebyte's Anti-Malware is my go-to anti-virus in WORST-CASE scenario, but even though their newest version is usable on XP, they are still working out the rootkit function bugs, so even though it can get rid of malware, it can be useless against rootklits at the moment. Going to their official site to check their responses and threads will show that they are working out bugs on 'rootkit option' checked and the full scan hanging up and stopping causing you to cancel and find alternative means.
AT this very moment, I AM running another Avast! boot scan, but this because of a mistake i made during the first one i believe... when you get to an option in the bootscan that asks you if you want to to remove/delete/'move to chest' a file that is located in 'temp' folder that is associated to Avast!, say no. That is my next plan, because the first time i did this I said yes and the scan stopped abruptly.
At this moment I can run my necessary programs and softwares on that PC where as before i could not. I can now run them no problem after the work I just did and explained but I'm not done until I completely clean my laptop. I will post this now and start the the thread and try to add as I go along. Hope this helps you out there.
P.S.: While writing this thread my Avast bootscan has gone farther now then before when it glitched when I said 'yes' to deleting the Avast! temp file. Deleting the Avast! temp file will stop the boot scan and cause you to hit the power button, then reload to desktop and go to the Chest and refresh it from the 'Chest' list.