PC not going beyond Login page in Windows 7

For the past couple of days I'm having this problem with me not being able to go beyond the login screen of Windows 7. Once I switch on the PC and after I enter my password in the login screen I'm shown the Welcome screen for long time. Infact yesterday I left it like that for an hour and still it was not moving beyond.
Later I restarted the PC and selected Safe Mode and I was able to get in. Of the several attempts made in one of the attempts when it did login it was giving an alert continously from Avast indicating that system need to reboot. Once I reboot I get some Command Prompt kind of screen which seems to clean/detect some files. Since it was taking long time I pressed Esc.

Could there be a virus which has infected my PC?

If you have backup for your important files, format your system and reinstall windows... And this time use a good security suite ( avira free av + Comodo firewall is a good choice).

check if you have any online services running, also check msconfig startup disable services which are not needed.

In safemode, create a new account and then check whether you still experience the problem.
If not, then as [MENTION=2132]RCuber[/MENTION] mentioned - it should be because of those unnecessary startups.

Sometimes malwares gets added to the startup, doing some unnecessary tasks - thereby slowing down the login.

seems like an issue with boot loader....

repair the boot loader

^^ not a boot loader issue as he can load up to Login Page.

One more thing which may not be directly related to this. I have 3 SATA HDD and one IDE HDD connected. I have data in all HDD i.e. drives which need to be backed up unfortunately.
For starters can someone help with when the system starts up how do I ensure I get the options do boot Via Safe Mode. Currently I'm plugging off the power cable and when I start the system by default I get the options like Start with Safe Mode etc since Windows was not properly shut down. I want these options to be listed when I log on. Is it F8 I need to press? When I do I get some other optons like Windows Vista Debug Mode.

Also during one of the times when I restarted the PC after an alert from the Antivirus upon restarting on the window I got a message indicating some virus infection although I don't remember the name of the virus infected.

- - - Updated - - -

Now I'm able to login and after everything is up I'm getting this message.
*s2.postimg.org/7tfktlgux/Avast.png
how do you print screen

Just press NO.
Install malwarebytes and fully scan your PC. Avast isn't that powerful IMO. Also download Malwarebytes Chameleon

For future proofing buy any good paid AV.(or use PC smartly

)

@OP, the same problem happened with me before. However the culprit was pending sector on OS drive. So I suggest you to run HDD self-test from Linux via flash drive and post your result.

Scanning using Avast helped resolve the problem.

When this problem happened I installed OS on another HDD now I see that I'm getting frequent Not Responding when I try to access the other drives or I try to copy Data from one external drive to another external drive. The PC Restarts by itself. Could this be the auto.inf file on the External HDD. I tried twice copying the contents of one external HDD to another.
Should I uninstall avast and install Avira anitivirus on this one. Could there be any virus on the external HDD which avast could not detect.