Helping people with computers... one answer at a time.
When installing anti-malware tools on your machine makes things worse, it's one hint that there may already be a deeper problem.
I followed your recommendation and installed Microsoft Security Essentials. It's been a nightmare ever since. Things are worse than before. I don't know how you can recommend something like that. What do I do to get this mess cleaned up?
I stand by my recommendation.
Microsoft Security Essentials is a solid anti-malware tool that works and works well in the vast majority of cases. I like it because it's a one-stop solution for a fairly broad base of protection and it's kept up to date by Windows Update.
So why'd it mess up your machine so badly?
I have a theory.
And I have some steps for you to try and dig out of this mess.
My theory is simply this: your machine was already infected with malware.
Malware these days is pretty sophisticated and part of that sophistication is that viruses and spyware will take steps to protect themselves. Most often, this is in the form of preventing anti-malware tools from running or updating, and perhaps even preventing you from accessing download sites where you might get anti-malware tools.
What I believe has happened is that the malware already on your machine seriously interfered with your installation of Microsoft Security Essentials. Either the installation was prevented or corrupted or the program's ability to run was somehow disabled.
In other words, the malware made a further mess of things.
That makes things kinda tough, because if you have an infected machine, one of the first things that you want to do is to update or install anti-malware tools to eradicate the infection.
But you can't clean the infection ... because the machine is infected.
Using a different machine, download the Microsoft Standalone System Sweeper and burn that to a CD.
Now, reboot your infected computer from that CD and run the tool to scan your machine's hard drive for malware.
Booting from that CD prevents the malware on your machine from ever gaining control and thereby stopping that malware from interfering with the anti-malware tool.
Which, by the way, is really just a version of Microsoft Security Essentials, in a stand-alone, boot-from-cd form.
My guess is that there's a good chance that the sweeper will detect and remove the malware that started all of this.
If not, I'd point you at How do I recover from a bad virus infection? for further, more aggressive steps to take to rid yourself of the problem.
Don't blame the messenger.
If there's malware on your machine, then all bets are off; it's not really your machine any more.
As such, that means that the malware could be responsible for all sorts of mischief, particularly making anti-malware tools fail or otherwise misbehave.
Microsoft Security Essentials is a good anti-malware tool. Because of that, it's very likely that malware would target it, not just to prevent it from working, but perhaps even to make it look bad.