Windows 7: Computer stuck at black screen with flashing white underscore

Today I started up my pc and after the BIOS screen (the place where you can press f8-f11 for various options) it went to a black screen with a blinking underscore in the upper left corner and stayed there indefinitely. It did this even after reboot.

I tried using the diagnostic tool and everything it tested passed (including HDD). I did this test twice and the same results were produced.

I also googled for similar problems (one topic mentioned that the op disassembling his computer and physically tapping a chip on the motherboard caused it to work) but I have no experience with taking apart my computer and i do not want to break it accidentally. I did however chance upon a topic advising him to do a CMOS reset which apparently helped that op, so i looked through the various options on the BIOS page. There was one option (f10 I think) mentioning CMOS on its fourth sub-window, so i pressed the reset option but I'm mot entirely sure if I used the right function.

I uninstalled kaspersky pure and replaced kaspersky pure for kaspersky anti-virus yesterday, dont know if this was the cause.

I am using windows 7 64 bit.

On you computers Motherboard there is a round battery. Remove it and put it back in and see if that helps.

You need to run chkdsk then run Startup Repair up to 3 times.

How to run chkdsk from the Recovery Console

• Boot your Vista or Windows 7 installation DVD
• When you see "Press any key to boot from CD or DVD", press Enter
• At the "Install Windows" screen, click on Repair your computer at lower left
• At the System Recovery Options screen, make note of the drive letter assigned to your boot drive (normally C: ) and click Next
• At the Chose a Recovery Tool window, click on Command Prompt. You will be sitting at X:\Sources directory
• Run chkdsk
  • If you did not note the drive letter of your boot disk, you can enter bcdedit and look at the osdevice line to see what it is.
  • Type chkdsk c: /r and press Enter (use the letter from above).

Let it run to completion undisturbed.

If you don't have a install DVD, you can download a legal copy here:
Official Windows 7 SP1 ISO from Digital River

Make sure you get the same version you have installed: 32 or 64 bit; Home Premium, Pro or Ultimate.

See here: Startup Repair

I can't remember if mine is premium, pro or professional. How do i check? Can't run dxdiag here or at least I dunno how to run it from the BIOS page. Also, must it the iso be burned into a CD? Can i run it from a HDD? I don't have cds or dvds with me.

Just curious, does anyone have any idea on what is possibly causing the problem?

You can't run it from a hard drive so you need to burn it to CD or make a bootable flash drive from the downloaded .iso.

See here for an easy way to create the bootable flash drive from a downloaded WIn 7 .iso image: Universal USB Installer – Easy as 1 2 3 | USB Pen Drive Linux

Select Windows 7 from the drop down menu (at the very bottom of the list).

You will need a 4+GB flash drive.

It might be easier to just buy a couple DVD+Rs.