Hi! Thank God I could find a USB mouse. But the strange thing is after plugging it, it would behave the same as the touchpad. I disabled the touchpad and then the mouse started behaving correctly. I turned on again the touchpad and it is now partially working (right button doesn't work at all). I also noticed that sometimes, some keys of the keyboard won't work, like the windows key. For example, I have my task bar hidden, and, in those cases, when I press the windows key, the taskbar will appear but the start menu won't. Usually, 1 minute later it will start working again.
Malware Bytes and Scannow (I used "verifyonly") couldn't anything abnormal. I tried using Dell Diagnostics, which will test everything, but it couldn't only test some devices like video card, hd, cd rom and a bit of the memories because I didn't had the utility partition ready. I was planning to test the touchpad and the keyboard.
I never uninstalled touchpad driver through start menu or control panel. As I didn't had a mouse atm, I went directly to device manager to uninstall it from there. At reboot, Windows installed it again. Nothing worked. I then uninstalled the driver again and "said" to delete it, so it wouldn't install it again at reboot. It didn't worked too. I'm currently only using Windows standard driver.
And sometimes, the USB mouse behavior is affected, as I said, by the strange touchpad behavior. How can that be?
Until I'm absolutely sure it is not a hardware malfunction, I will not attempt a system repair or even a reinstall, as the last repair attempt went so badly (dell factory recovery partition as well the repair cd were corrupt) that I had to reinstall everything, downloading the OS from the internet. This was 2 weeks ago. The reason for the repairing was a BSOD by an unknown cause, which was later discovered to be ZoneAlarm firewall. I changed to Comodo then. Avira is just a temporary antivirus, as I have an one year license from McAffe.
If nothing gets better until Monday, which probably won't, I will call Dell international services and discuss what can be done.
In the mean time, I might try older restore points :-)
Thank you for your help :-)