Guest system window too small (Centos 6.9)

[zfang]

Hello, I am using VM 4.3.12 with the host of windows 7 and Centos 6.9 guest.

I can not adjust the window even after I installed the guest addition successfully.

My monitor's resolution 3480*2160 .

The guest system maximum shows 1024*768.

Is there a way I can to fix that ? Thanks.

[socratis]

Hello, I am using VM 4.3.12 with the host of windows 7 and Centos 6.9 guest.

VirtualBox 4.3.12 is way too old, you need to upgrade it. The current version is 5.2.12.

The guest system maximum shows 1024*768.

That sounds like the Guest Additions were not installed properly (at a first reading).

1. Uninstall VirtualBox. Your VMs are going to be untouched. Reboot.
2. You may want to clean up your registry and/or filesystem at this point. CCleaner is a freeware utility that could help you. Mind the installation, it comes with "offers" from 3rd parties, known as "bundleware". Also, check out Device Cleanup program that helps you to remove any unused devices from your computer, mainly multiple "Host-Only Adapter #n".
3. Download (if you haven't already) the latest VirtualBox and its matching ExtPack. Store them in a common location, i.e. not on "Desktop", or "Documents", but to "Public/Downloads" for example.
4. Uninstall (don't simply disable) all 3rd party antivirus. If you're afraid about your computer being vulnerable, pull the Ethernet plug, disconnect your WiFi, don't go browsing around.
5. Locate the downloaded file in Windows Explorer. Right-click on the installer and select "Run-as-Administrator", even if you are the administrator. At the end of the installation, choose to "Start Oracle VM VirtualBox". Do not worry if your VMs do not show up.
6. If you're going to install the ExtPack, go to File » Preferences » Extensions. Click on the icon with the orange, down-pointing arrow on the right. Select the ExtPack from the previous steps.
7. Quit VirtualBox. Re-start VirtualBox as you would normally, i.e. from the Desktop shortcut or the Start menu.
8. Update the Guest Additions (GAs) in your guest(s).