To be clear: Windows starts up normally, right? As in, it doesn't immediately force a reboot?
The real CSRSS.exe program is a very
critical part of Windows. So critical, in fact, that if it's not found Windows will force a reboot. It is a common trick, however, for malware to use the name CSRSS.exe so as to appear legitimate to casual observers. The fact that the missing CSRSS.exe is located not in C:\WINDOWS\system32
but rather in a directory under your username (possibly the Temp folder) reenforces the notion that this is (or was) some bit of malware.
The good news is that the malicious CSRSS.exe could not be found and executed. It may have been quarantined by your anti-virus or deleted from the Temp directory (since it's only intended for temporary files anyway.) The reference in your system's startup settings to this file still exists, which is why Windows is complaining that it can't find it, but the actual file is gone.
Run a full scan with your anti-virus, being sure to get the latest updates to the scanner definitions. Let it clean anything it finds. For good measure you may want to run an additional scanning tool such as Malwarebytes Antimalware
(free for personal use.) Think of it like getting a second opinion from another doctor.However
, if you have noticed other signs of potential malware activity (your Google search results are being redirected, odd warnings that entice you into downloading and/or purchasing some software to correct purported system errors, etc.) then you would be well served to start a topic in the Am I Infected? What Do I Do?
forum detailing all the suspicious and unusual symptoms you have observed.