"Unsludging" a Windows 7 laptop?

I apologize in advance for a long post that follows. I'll start with the questions, and then flesh out the background.

The questions surround what to do with an Asus laptop, purchased in 2011, Win7, good specs (2+ GHz processor, 4 gigs of memory), and operated in a sensible and "safe computing" way (have never detected malware on it), that still seems to take forever to boot, to log in, or to launch programs.

Not sure if the answer is some surgical procedures to the computer and registry, or if it's somehow possible to reinstall Windows without trashing the installed programs and necessitating that they too get reinstalled.

Okay, that's the simple part. Here's the longer background.

The first problem we had with the computer, yet to be solved, came almost three years ago, six months after purchasing it, where suddenly it failed to recognize or be able to access other computers on our home network, that it had been able to. All was fine one day, then the next day it wasn't. Laptop can no longer access shared printer/files on home network, and several threads chained to it by me, document this into the ground.

Otherwise, other than some sketchy power issues that now have been under control for a year - the laptop-based connector for the power cord shorted the machine out and had to be replaced - it's mostly been fine.

The laptop has five different accounts on it. I have one, and it's been passed from one daughter to another, to my wife, and we've been too "afraid" to delete the old accounts. Plus there's an account for the computer shop we take it to, so they can have access to the computer, without being in anyone else's stuff (yes, I realize that this account, with administrator privileges, can go anywhere on the computer).

I am sure that doesn't help make it lean and mean.

Over the past six months or so, the computer has seemed to get slower and slower. The Asus "splash screen" at startup comes and quickly gives way to the "starting windows" screen, but then that lingers for 1-2 minutes (my own home and office computers are several times faster than this), then the login sequence seems to take roughly a minute, sometimes more, versus the near-instantaneous logging in I see on other computers. Clicking on an icon to launch a program - browser, Microsoft Word, whatever - can take a minute or more to launch the program. Youtube or Netflix performance was sketchy too, as if the buffering wasn't working.

In the past couple days, I made two discoveries about the laptop (which, again, my wife uses, and I almost never touch).

One was that the hard drive, partitioned into a C and D portion, was almost full on the C partition. I'm sure this explained a lot of the slowness. The 80 gig partition was about 95% full and probably more.

I used EASEUS Partition Master to resize the partitions, taking about 100 gigs from the much larger D partition, and assigning them to C.

The other discovery was that the Windows Updates had been failing. After some successful updates on 8/13, there had been failure after failure since, and launching Windows Update put me on a screen with a red error warning. It could find updates, but then I'd get an error 0x80070005 in trying to download them.

Tried several things with the registry that I read on this forum, and none worked. Finally I used the FixIt tool that Windows help was pushing to me, and that took 30 minutes or so, but it fixed things. I had 37 updates downloaded and successfully installed, so all good there.

But the computer remains slow to boot and login, as described above.

I doubt it's malware. My family is well above average in practicing "safe computing," and I have never found malware on this computer, although I admit I haven't scanned in the last six months.

I ran an sfc /scannow on the computer and all results were normal.

Same with a chkdsk at boot.

Ran ccleaner on the registry, and it cleaned out a lot, with no noticeable speed improvement.

Cleaned out a lot of temporary files, but no notable improvement.

Would a defragging help? I'd imagine that with the C partition 95+% full prior to my expanding it, a lot of key files are very noncontiguous.

And as I asked before, is there a comfortable way to reinstall the O/S, without having to then reinstall all the program files and software on the computer?

Any ideas for speeding this laptop up, to what I remember it being, I'd appreciate.

Thanks.

Thanks for guiding me to the clean reinstall tutorial. That thing is beautifully written. Good help.

If I tackle that - which should be very doable given the thoroughness of the tutorial - I'll do so during the week after Christmas, a good "downtime" time.

But of course I'll spend the intervening few weeks hoping against logic that there's an easier "magic bullet" out there.

If you have any other questions, including about finding programs you need and rely upon to reinstall, then let us know.

There will be no need for a computer shop to have its own account on your PC once you have the one great perfect install using only the tools and methods given in the tutorial.

Update... in applying the "diligence" part of "due diligence," I ran Malware Bytes on the computer and it found 150+ instances of malware and quarantined them. Despite this, the Windows Firewall still won't start, the relevant MS FixIt tool for that recognizes but cannot rectify that problem. Oh, and yada yada yada.

Yes, my head, which is what I usually listen to, tells me that the reinstall will be great for the computer, and I'll of course be empowered after accomplishing it myself, and there are great resources on this forum, and I'd not "be alone" through the process, and all.

But my heart had me call my favored repair place, and they're quite optimistic that they can complete the cleaning of it (I've never ever had to "go outside" for malware removal), and that will fix things. And they've always been very "plus plus" in terms of doing much more than they initially set out to do, at no additional cost to me.

Yes yes, I know... Pathetic Wimp, thy name is me.

Still, I'll update when I get the computer back from the shop.

I had never before paid someone to take malware off my computer. I know how, and in general we practice pretty safe computing in my family.

But the laptop was originally used by a 15-year-old, and I am guessing that led to its original infection - something that happened three years ago!

My trusted computer repair place did malware removal, obviously better than I had, and the thing works like a charm - including the network printing capability, lost three years ago, being restored!

Now, for your last step, get a report from the repair shop regarding what they did, and forward a copy on to us. Let us add to our knowledge.

I'd like to know what the problem was...