I need a good clean software and driver diagnostic tools

Your "slow internet" may be unrelated to your PC or any driver issue. It's tough to say without a lot more detail.

I would generally be wary of "diagnostic" software.

The most commonly recommended malware tool is Malwarebytes from malwarebytes.org. The free version will remove malware. The paid version attempts to prevent it from ever getting on your PC. I think it's about $20 a year.

CCleaner is easily the most frequently recommended all-purpose "cleaner". It's free and conservative, not highly invasive. It has a registry cleaner function that most would tell you to avoid because registry cleaning is very rarely worthwhile and has some small chance of causing problems.

Bloatware: I'd investigate what unused or unwanted programs were on my hard drive and simply uninstall them.

Boost speed: I'd be wary of anything that said it could boost speed. Concentrate on basic maintenance and don't try to hit home runs.

Driver issues: I'd try to concentrate on that specifically rather than look for a "fix-it" application. I would generally NOT replace known working drivers even if they are "outdated".

You can use Task Manager for some of that. Look at the processes tab. 50 to 70 processes is normal. If you have a lot of applications installed and running, that may amount to 90 or more processes.

Type "msconfig" into the start button search box and follow the link to msconfig.exe. Look at the services tab. Check "hide all Microsoft services". I currently have only 7 non-Microsoft services shown as running. Some people have 20 or 30.

Look at the startup tab in msconfig. How many things are checked? Anything checked will run whenever your PC is started, but Windows will start and run with NONE of them checked.

Look at your list of programs from the start button. How many of those haven't you used in the last year or maybe ever?

I agree with ignatzatsonic. Anything that tells you it will "speed up and optimize" your system is highly suspect. Ccleaner is a top choice and highly recommended for system clean up. If you're worried about drivers ... Click Start,in the search box type Device Manager and click on that. Any yellow triangles/exclamation marks you see are driver's that NEED fixing. If you see any, right click on them and choose update.
If you do need drivers , and Device Manager won't download them, check with Dell first. They have a auto-detect utility that will scan your machine and show you what you need. Here's a link :Support | Dell US

As far as optimizing your machine to get all the speed you can out of it, theres nothing better than following these tips in our tutorial for that : Optimize Windows 7

Also, I find that PC Decrapifier helps the more inexperienced user decide what can be removed from their systems, https://www.pcdecrapifier.com

Bear in mind that "slow internet" can be many things or even a combination of many things.

Uninstall using Catalyst Control Centre. Uninstalling from device manager only removes CCC. It doesn't remove the drivers that are installed.