Windows 7 My computer drastically slowed at once

used Ccleaner

used avast anti virus scan (quick)

used avast cleanup premium

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CCleaner is malware, as it is owned by Avast, which spies on the Device ID, Date, Hour, Minute, Second, Domain, Product, and Behavior of shopping activities from their antivirus customers. Use a Microsoft Defender Offline Scan instead. Avast is clearly an ineffective antivirus, or it would have detected and destroyed itself already.

Recently I ran into a BSOD loop which made me restart my computer many many times by hand because sometimes my computer froze instead of showing BSOD, now after I managed to fix it my computer is REALLY REALLY slow, tried so many things

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Forcing your computer off multiple times could have corrupted the SSD. Unlike HDDs writing directly without interfering with surrounding data, SSDs erase and rewrite megabyte-sized blocks when any contents within are modified, storing blocks in volatile cache while rewriting. If the power is cut while writing to most consumer SSDs, blocks being rewritten will be destroyed. If those blocks contained the mapping tables, the entire SSD can be bricked. Repeated incidents after initial damage to the mapping tables can cause corruption to become more extensive. That's because mapping tables are relatively inactive, but receive increased writing activity while repairing initial damage, so have an elevated susceptibility to further corrupting on repeated power loss.

Many newer SSDs claim to have Power Loss Protection, but that is rarely sufficient compared to what HDDs provide. That's because the volatile cache is considered "data in transit" even though it may contain previously written data, which would not be in transit with CMR HDDs. Existing data only happens to be in rewritten blocks by random chance, which is outside the user's control. HDDs have circuits capturing spindle momentum to swing the actuator arm off the pristine platters during power loss (as described in US Patent 6,025,968). Only SSDs with large tantalum capacitors, such as Intel PCIe server cards and Seagate IronWolf Pro boxes, are sufficiently protected.

I will really appreciate any help and feel free to ask questions.

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1. Run a Microsoft Defender Offline Scan.
2. Backup your files to an external HDD.
3. Download a Windows ISO and double-click to mount it. If it doesn't appear as a drive, log out of Windows, and log back in.
4A. For Windows 10 ISOs, input DISM /Online /Cleanup-Image /RestoreHealth /Source:X:\Sources\install.esd into an administrator Command Prompt, replacing X with the letter of the ISO drive.
4B. For Windows 11 ISOs, input DISM /Online /Cleanup-Image /RestoreHealth /Source:X:\Sources\install.wim into an administrator Command Prompt, replacing X with the letter of the ISO drive.
5. Use sfc /scannow in an administrator Command Prompt.
6. If the problem persists, double-click Setup.exe inside the ISO.