Various problems, possible drivers/services broken or missing

I've started having various problems cropping up for a couple month now.. Among them being:
Periodic, random de-selection of the current active window, rendering it seemingly unresponsive to input until clicked on again.
"The Windows Security Center service can't be started."
"windows Update cannot currently check for updates, because the service is not running. You may need to restart your computer." Upon looking for fixes, I noticed that I don't even HAVE the windows update service anymore.
Every time on start-up, an error appears, so soon that the desktop hasn't even appeared after logging in, claiming that string.dll is missing.
Cannot turn Windows Firewall on, as once I attempt to do so I get the message "Windows Firewall can't change some of your settings. Error code 0x80070424"
Also: "There was an error opening the Windows Firewall with Advanced Security snap-in" ... "The Windows Firewall with Advanced Security snap-in failed to load. Restart the Windows Firewall service on the computer that you are managing. Error code 0x6D9."
Task manager used to fail to start. "The program can't start because pcwum.dll is missing from your computer. Try reinstalling the program to fix this problem."
Right before my last system restore, various drivers went missing or were broken, including, from what I remember, the one that my adaptor uses to connect to the internet. I could not connect either wirelessly or via direct connection with the ethernet.
I'm afraid to restart my computer, lest the drivers break again...
Also I tried running a virus scan with AVG while the internet drivers were broken, and apparently it said I'm missing a driver to scan too? I have no idea >.< AVG isn't on my computer atm anyway..
I also never received the disc with the operating system on it when I got the computer, so it's not like I can do a complete reinstall or get the missing things from there if that even is an option.
I've tried running the 'sfc /scannow' thing, and it supposedly fixed everything it could, however nothing changed noticeably.

You are infected with something. Use another computer to download and then burn and run virus and malware scanners.

How might I do that? Is there a scanner you would recommend? I have used Malware Bytes, which turned up nothing last i scanned, so..

You need to do Offline scans. Make a Boot CD/DVD or USB Thumb of the tools and run them from booting from the CD/DVD or thumb drive you make of the Offline scanners.

Malware bytes has a offline tool and check the Tutorials on this site for virus scanners. Try the Win Defender tool.

Microsoft

Win Defender Offline did not work, I tried 4 different times, on two different computers, but every time it turned up an error, saying there was a problem preparing the flash drive or something.
Malware bytes' scan turned up clean, and I disinfected my computer using "ad-aware" that my friend uses, removed 11 items..
However there does not appear to be any change.

LeoLeonardoIII said:

I also never received the disc with the operating system on it when I got the computer, so it's not like I can do a complete reinstall or get the missing things from there if that even is an option.

You CAN do a complete reinstall IF you have the 25 character Product Key, which should be on a sticker on the PC.

ignatzatsonic said:

You CAN do a complete reinstall IF you have the 25 character Product Key, which should be on a sticker on the PC.

Is that so? What would that entail? How would I do this? Is there any significant risk to doing a reinstall like this? I just checked, and I DO have the product key sticker in place still.

How far back can you do a system restore?? Just throwing it out there.

allen1979 said:

How far back can you do a system restore?? Just throwing it out there.

The earliest there was one for 9/18/2011, 4:23:22 PM
I would have used that, but..

The selected backup could not be found. System restore is looking for a restore point that is on your backup. Choose a different restore point.

When the internet died entirely for me, the only way I got it back up was by using a system restore for 11/01/2012 (the very beginning of this month) and as of right now that one does not appear to exist anymore.
So no, I've looked into system restore but it does no good, unfortunately.

sorry to hear that. If you have a backup, or a copy of your operating system you could do a fresh install. thats the best i got.
Oh, yea, like someone else mentioned, get some antivirus from somewhere else, and use a flash drive to put it on your computer. i use avast free, and it works well.
but as for you missing dll's? i got nothing, i would be doing the same as you
good luck