OMG! My Win-OS desktop or laptop system has been cracked!?!
The common term used for a compromised system (software, app, etc.) is "Hacked"... but actually, Hackers are the good-guys. The "Crackers" are the bad-guys, as they use stealthy methods to "Crack" into your system (app, device, etc.).
Now what do you do?
The first two things I do when I encounter a Windows OS machine that I suspect may be compromised in some way is to run:
AdwCleaner
Now by "Malwarebytes"
Run it once... reboot when prompted.
Always be sure you have the current version before you run it. (i.e. If it has been several days, weeks, months since you last ran it, download a new copy).
You do not install this software, you simply run it from the "<filename>.exe" download.
Then I run:
CCleaner
By "'Piriform"
First do a basic clean ("Cleaner"), using the defaults.
"Analyze"... then "Run Cleaner"
You may have to do this 2 or 3 times (or more).
After several tries... If the same few files (usually 2 or 3, maybe more) keep popping up after a cleaning, just ignore them.
Then Clean / Repair the "Registry"
"Scan"... then "Fix"
Always, always, always backup the Registry before you "fix" it. A corrupted registry will cause your entire system to fail. I always setup a folder just for this function. CCleaner will remember that location after the first time you choose it.
This backup prompt is typically "ON" by default. So... If you are not prompted to backup the registry every time, check the settings and turn that "software switch" (typically a checkbox) "ON".
Hopefully you never need to do it (it is "bad news"), but if you do, search: Restoring the Windows Registry
ADWcleaner may do some Registry fixes, but CCleaner will do more.
I always run AdwCleaner first, because it can catch AdWare and similar items that CCleaner will not find.
I also suggest turning "off" the "Monitoring" function in CCleaner, especially if you have an older machine, or one already low on resources, as this "background function" will further slow your system down.
CCleaner also has a nifty feature that will easily allow you to control (disable / enable) "Startup" apps that run in the background. Turn off anything you do not absolutely need to have loaded on startup (from a cold or warm boot). You can always launch it manually if you need to. This is especially helpful for those annoying pop-up windows that mysteriously start appearing one day, for no apparent reason. (There is a reason, you probably just did not notice what you did to initiate the change. Tech's call this "operator error".)
As ALWAYS... When installing anything, especially "free" software... Read the Fine Print (or: RTFM)... and... Be Careful What You Click On! .... Be sure to be on the lookout for obscure "check-boxes" and "option buttons" (often cleverly embedded in the "agreement" section or "license" text) that need to be de-selected in order for you to avoid installing a lot of "crap-ware" (PUPs) associated with your nifty new "free" program.
"The Large Print Giveth... and the small print taketh away."
Beware!!!
DO NOT download and install CCleaner from FileHippo... ironically, this version typically installs a lot of "PUP's" (Potentially Unwanted Programs), which you then need to turn around and remove. They are usually harmless, just a nuisance. (TANSTAAFL!!!) The way I usually do it to be sure I do not get to the FileHippo site is to hover/click over "Download" at the top of the Piriform page, then (left) click on "Download CCleaner", then click on the "Free" button. To be sure, always hover over the link first, then look in the (typically) lower-left corner of your browser to see the pop-up, which will show you the URL you are about to activate / travel-to. If you see "FileHippo" in the destination URL, try again till you get it right (from the source, which is Piriform).
Then, thirdly, you want to be sure your Malware Scanner is up-to-date, configured correctly (the "defaults" [settings] usually work fine), and run a thorough (deep) system scan (which can take hours, even overnight). I suggest using the embedded malware scanner provided by Microsoft. Earlier versions (up to Win-7) are called "Microsoft Security Essentials". Later versions (Win-8 & 10) are called "Windows Defender"... (this is a somewhat loose rule in nomenclature, but it applies for now).
If running these programs as described above does not solve your problem, then you will need to accurately identify the "infection", if it still exists... do a web search on it (from a clean system), and follow the instructions for removal. "Accurate Identification" can be tricky, and take some time. Choosing the right keywords to search with usually requires some experience, and/or patience.
After that, it the problem still persists, you will need to take the machine to a service center and get it professionally cleaned / fixed. You can call a tech out to your house, but that will cost 2x to 3x as much, and they will not do as good a job as you would get if you take it into a shop.
I ALWAYS recommend independent, locally owned shops first. "Big Box" shops (Best Buy, Office Depot, etc.) usually are a rip-off.
Good Luck!
You can find links to the above Software Suggestions here.
:-)
You may also want to check-out the sections here on: Malware ... Daily Use ... and Basics
:-)