Computer extremely slow

Two days ago when the laptop was shutting down I accidently removed the AC Adapter( I wasn't using the battery) and like you might imagine the computer shut down. When I turned it on again, it showed me the three usual options and I selected the normal way.
After that my computer is taking more than 5minutes to fully start up, my browser and windows explorer is constantly freezing and just now it took 5 minutes to show the message "Welcome" and after finally starting it showed a message in the background that one windows service didn't turned on which is Windows Aero. Anyway can help me fixing this issue please? :)

You may have some damaged or corrupt system files. I'd try running a System File Checker scan from an elevated command prompt (option two.) If problems are found run the scan 3 times rebooting in between each scan.

SFC /SCANNOW Command - System File Checker

If that doesn't fix things I'd next try a Startup Repair. Again, if problems are found run the scan 3 times rebooting in between each scan.

Startup Repair

If SFC and Startup Repair haven't fixed things, I'd consider a Repair Install. This would be pretty much a last attempt at repairing prior to completely erasing the hard drive and doing a clean install.

Repair Install

marsmimar said:

You may have some damaged or corrupt system files. I'd try running a System File Checker scan from an elevated command prompt (option two.) If problems are found run the scan 3 times rebooting in between each scan.

SFC /SCANNOW Command - System File Checker

If that doesn't fix things I'd next try a Startup Repair. Again, if problems are found run the scan 3 times rebooting in between each scan.

Startup Repair

If SFC and Startup Repair haven't fixed things, I'd consider a Repair Install. This would be pretty much a last attempt at repairing prior to completely erasing the hard drive and doing a clean install.

Repair Install

So far I did SFC and Startup Repair and I didn't found any problems but when the SFC made it to 100% complete my computer froze, I tried to start Windows Task Manager and I ended up in a black screen with this message "failure to provide security and options of closure".

Couple more things to try to eliminate problems. Possible that something installed on your computer (an application or program) is contributing to the problem. You could try running a Clean Startup (aka Clean Boot.)

Troubleshoot Application Conflicts by Performing a Clean Startup

Also some general troubleshooting steps for Windows 7

Troubleshooting Steps for Windows 7

And some additional troubleshooting for failure to start issues. Yes, I realize you can boot your computer, but many of the troubleshooting steps can pinpoint specific areas of concern like Safe Mode, Restore Points, etc.

Troubleshooting Windows 7 Failure to Boot

I want to give some quick updates: I did everything the post above said but it didn't made any difference like I was expecting, now what appears to have fixed my problem was the rollback of some drivers that I had updated a few days earlier before this started to happen. The results are good, my boot is normal again no more slowdowns in the "Welcome" screen and so far I haven't experienced any freezes.

Good news, indeed! Thanks for posting back.