I have a Dell inspiron 1545 running Windows 7 professional and I have recently fallen victim to a Trojan virus that has somehow managed to surpass AVG, ZoneAlarm and Malwarebytes too!

I have tried running full scans with all 3 security programs and the Trojan keeps coming back so now it’s the final straw for me.

What I am kindly asking your help for is how can I completely wipe the hard disk drive 100% and also how to completely remove the OS and reinstall it.

Basically I want to wipe absolutely everything from scratch but I have no idea where to start?


3 Answers 3


Where did you see the warning?

Clean Installing Windows 7

Warning: all data on hard disk will be destroyed. Backup if necessary

  • Change boot order in BIOS.

    Turn on the computer. When the BIOS screen appears, press Del , Esc , F2 , F10 , or F9 (depending on your computer’s motherboard) to enter the system BIOS. The key to enter the BIOS is usually shown on the screen. Navigate to the BIOS's boot options menu.

Select the CD/DVD drive or USB drive as the first boot device.

Insert the Windows 7 disc into your disc drive or boot able flash into a USB port.

Save the changes of the settings and restart (option in the last tab in BIOS).

Start your computer from the disc. After you have placed the disc into the disc drive, start your computer. When the computer starts, press any key when asked press any key to boot from CD or DVD

  • After you choose to start from the disc, Windows Setup will begin loading.

Choose Windows Setup options like language and locale. Once Windows Setup loads, you'll be presented with a window. Select your preferred language, keyboard type, and time/currency format, then click Next. Click the Install Now button.

  • Accept the License Terms shown. Read over the Microsoft Software License Terms(EULA) and check I accept the license terms, and click Next.

  • Select the Custom installation.

Decide on which hard drive and partition you want to install Windows 7 on. If the hard drive has data on it, delete the data off of it, or format it.

Select the hard drive partition from the list.

Click Drive options (advanced). Click Delete partition from Drive options. And repeat this for all your partitions. Now your computer doesn't have any partitions yet, create as much as necessary by following below step:

  1. Select the hard drive from the list of hard drives.

  2. Click Drive options (advanced).

  3. Select New from Drive options. Select the size, and click OK.

    • Installing Windows 7

Once you've decided on where to install Windows, select it and click Next. Windows will begin installing.

Rest steps are pretty direct forward. Install your device drivers and other software after setting up everything.

Install security software. Windows firewall is good enough to protect you. But do not install multiple AV with real time protection enabled Free alternatives to AVG are Avast or BitDefender .

I suggest to keep MBAM. MBAM's realtime components are enabled only if you activate the premium version.

  • Could I do this with a Windows 10 CD ?
    – amx128
    Sep 19, 2015 at 0:56
  • Yeah. You asked for Windows 7 in question, so was the answer. Options in Windows 10 may have slightly different naming.
    – Nikhil_CV
    Sep 19, 2015 at 0:58
  • Thank you very much , I will go with the Windows 10 install. If I do as you suggested, will that get rid of the virus for sure ?
    – amx128
    Sep 19, 2015 at 1:04
  • Deleting the partitions and formatting should remove all data and boot records from your hard disk. So, the reinfection case is very narrow. You haven't told what the infection is or how did you detect it.
    – Nikhil_CV
    Sep 19, 2015 at 1:07

Honestly, if an antivirus isn't removing malicious code properly, and assuming you have the scan for rootkits option enabled, you should assume the (second) worst, i.e. your boot sector is infected. Safe mode won't help against that. If you're upgrading to Windows 10 anyway, Do that first, and make sure you grab a copy of the ISO as well. If you just do a clean install, your Windows 7 key won't work.

After you've got a copy of whatever Windows you want, also get a copy of low level wiping/formatting software, like DBAN or GParted. This will ensure your boot sector is erased. Put the two of them on a (or two) USB Boot Drive.

Set BIOS to load the USB first, and the HDD not at all, and then reboot, with either the disk with your disk wiper on it, or a multiboot disk, depending on how you set them up. You should now be able to wipe the whole disk (no need for the multiple overwrites, just one will do).

Reboot again when you've finished wiping, and now, create a new system partition, and install windows on it. Mission complete.

When you've done that, make sure to reinstall all the security software. As well as Antivirus (you shouldn't have more than one active one, Malwarebytes is on-demand so it doesn't count), you should also be looking at Antispyware and Anti Exploit software, as well as a decent adblock for your browser, or a decent HOSTS file (malvertising sucks). That's all.


First of all, how do you know you are infected with a trojan???

Anyway, formatting is easy, but you will lose all your data.

I suggest you to go to your avg, then do a full scan:

  1. Open the AVG Program.
  2. Click the "Update now" button to make sure that AVG is fully up-to-date.
  3. Click the "Scan options" button.
  4. Click the "Change scan settings" link (blue text) within the "Whole computer scan" button.
  5. Make sure that all available check boxes are selected (except the "Scan for Tracking Cookies" option).
  6. Click the "Additional scan settings..." link, and then click All file types.
  7. Click "OK", and then click "Start scan".

It's better to do this in safe mode (restart, then press F8 or Shift+F8 to start in safe mode).

If your problem persists and you want to format (I'm giving you a link with pictures) it's much easier for you to follow the instructions. Once your hard is formatted (keep notice you won't get any confirmation on Windows 7 after format is completed). You should insert your Win 7 disk and follow the instructions.


Not the answer you're looking for? Browse other questions tagged .