It has been my experience that the "error creating temporary file" messages appear when the temporary file directories are incorrectly specified in the registry, or the directory is present but has a permissions problem that renders it inaccessible:
A few things to check:
Verify the %systemroot%TEMP directory exists on the computer, and that the SYSTEM and Administrators groups have Full Control of it in the Security tab of the properties for the directory.
Verify the %userprofile%AppDataLocalTemp directory exists on the computer, and that the the SYSTEM and Administrators groups and the currently-logged in user (i.e., the one %userprofile% belongs to) have Full Control of it in the Security tab of the properties for the directory.
Verify the %systemroot%TEMP directory is listed as the path for the environment variable TEMP under the [HKEY_LOCAL_MACHINESYSTEMControlSet001ControlSession ManagerEnvironment] registry key.
Verify the %userprofile%AppDataLocalTemp directory is listed as the path for the environment variable TEMP under the [HKEY_CURRENT_USEREnvironment] registry key.
If neither directory exists, recreate them. If neither registry key exists (or points to a different location), create or edit them to point to the correctly locations on the C: drive. A reboot will be necessary for the changes to take effect to the system.
If problems still occur after the reboot with updating, the file system on the drive may be corrupt. Performing a Chkdsk operation usually fixes this.
As for the uninstallation error, this can occur if there is a permissions problems on the %userprofile%AppDataLocalTemp directory. Hopefully, steps #2 and #4 above will fix that, but if not, you can use the ESET Uninstall Tool to perform a manual uninstallation. It can be downloaded from the following location:
ESET Knowledgebase Article #2289, "How do I manually uninstall my Windows ESET product?"
For what it is worth, I usually see these kinds of errors when someone either (1) installs a SSD and changes the temporary file directories incorrectly in an attempt to move them off of the SSD; or (2) runs some kind of "performance/cleaning/optimization" program that deletes a bunch of registry keys, directories or files in an attempt speed up the system, but ends up damaging it, instead.
Regards,
Aryeh Goretsky