OK, first things first - back up your own data. This is the valuable stuff on your computer ! All your work - documents, spreadsheets, graphics, whatever. All your photos and anything else YOU have created or stored on the computer. Depending on the quantity you can use DVDs (4.3 Gb each) or a USB hard drive ( up to 2Tb + ). Once you have done that, you can relax - disaster has been averted !
Next, you can try uninstalling recent updates. 'Start / Control panel / Windows update'. At the top left of the screen, click on 'View update history'. This will give you a list of all the updates your computer has attempted to install, and tell you whether the install was successful or not. Take a note of any it says were unsuccessful.
At the bottom left of the screen, click on 'View installed updates'. This brings up a list of all the installed updates. If any updates from the first screen appear in this list, click on them and then click uninstall ( at the top of the list ). I would be inclined to uninstall all of them back to the date this problem first occurred. Then re-boot and see if you are running normally.
If this doesn't work, then - unless anybody else comes up with a better idea - I think you are looking at a system re-install. This may be tedious but you have backed up all your own work so you are just looking at the operating system and your applications. There may be an easy way to do this since you have a laptop, and a lot of laptops come with a built-in recovery partition. Possibly the simplest way to check if you have one or not is to check the manual, and if you don't have a copy you will find one on the Dell web-site - just enter the model number for your laptop in their 'Support' section and download the manual.
If you have a recovery partition, look at the boot screen when you start up - that's the one with the Dell logo that appears as soon as you start up - and you will see an entry for 'Recovery', it's often F2 but there is no set rule about this. Again, the manual will tell you. Press the relevant command at the boot screen and the computer will go into recovery mode. You will get warnings that this will cause loss of date, just keep clicking 'Proceed' until it starts restoring, then go and put the kettle on.
When it has finished, your computer will be restored to the condition it was in when it was first sold. You will need to uninstall any software you don't want, install your applications, install all the updates to Windows since the date of the build, and put all your own data back.
If you don't have a recovery partition, then you will need a Windows install disc. As I understand it, so long as you have a valid registration key you can use any Windows disk to do the re-install, and the registration key should be stuck to your computer somewhere. Again, you will have all the applications to install, but this time you will probably also need to get drivers for your video and sound and other motherboard drivers, but you can get these from the Dell web-site. This is not particularly difficult to do, just seriously tedious.