Dell Optiplex GX1

[lindap]

It won't boot up. Error message says the following files are missing or corrupt.
C:\WINDOWS\HIMEM.SYS
C:\WINDOWS\DBLBUFT.SYS
C:\WINDOWS\IFSHLP.SYS

[goomnaga]

Reinstall your Operating System

[coolraj003]

I don't think you will need to reinstall the OS, just do a repair install and the missing files should be replaced from the disk itself. I do hope you have your data backed up though, just a recommendation.
Repair Install should be more than likely enough to take care of your problem.

Raj