RE: Registry cleaners-good or bad?
1. I use CCleaner regularly on a few machines, primarily in conjunction with Windows Disk Cleanup to get the garbage off the system drive. Their registry cleaner has never caused me any problems but in reality it's almost never actually necessary.
2. If the new BIOS does not resolve an issue you are actually experiencing (check the release notes), then generally speaking I would not upgrade.
3. In my experience updating using the Intel network software directly from Intel is safe, however it's usually unnecessary. Unless you have a very new NIC (wired or wireless), you are probably already running the latest available driver. Check here to see if there's actually a driver update for your NIC in the latest package or not. It's for Wireless only, I can't find one for wired:
e.g. for the 2230 card, driver 188.8.131.52 is the latest that supports it, even though the absolute newest driver is 184.108.40.206. The actual Proset package version doesn't matter.
You likely don't need any of the advanced services stuff in the Intel Wireless Proset downloader, so if you already have the latest driver, there's no need to install. If your card is not listed, it's no longer supported and you definitely have the latest driver from Windows Update.
For wired, again unless it's a very new card Windows Update should give you the latest driver. You do not need the Proset software unless you're intending to do advanced configuration with VLANs, teaming, etc.
If you do decide to update, make sure you that you download the latest versions of the Dell-supplied drivers ahead of time in case you need them. I sincerely doubt there is any value in messing with a wired NIC, but I have seen wireless drivers resolve problems with certain kinds of access points and security protocols on older cards. If you aren't having any actual problems with networking, it's probably best to leave well enough alone, but I think this is handy information to have if you do run into any issues.