Hello Forum: I am running a Dell Inspiron 560 with Win-7 SP1 , 64 bit, 2.70 GHz dual core processor, 4 GB RAM   500GB hard drive

The problem: I recently ran Disk Cleanup and Windows showed me deletable old files.  OBTW, I never delete the SP1 service pack backup files (920 MB) but I usually delete any old Windows Update files and any other small files that Disk Cleanup identifies. On my last Disk Cleanup Windows showed an unusually high 452 MB of OLD Windows Update files. Since I have deleted them SUCCESSFULLY before I figured it must be OK if Windows says it is. I deleted the old Windows Update files. BAD move. All new Windows updates failed to install. I TRIED 5 times. I got the error code and went to Microsoft site and had to download the System Update Readiness Tool. Coincidentally(?) it was around 450 MB. Once the tool was installed I was able to download current updates.  Now I am a little afraid to delete any old outdated updates with the Disk Cleanup function. Not looking to repeat the same mistake. I tested the Disk Cleanup utility after I successfully downloaded and installed the latest updates and it is now showing about 70 MB of old updates that I can delete. I have not done it yet since I don't want to delete something that is necessary. Looking back I guess I should have used System Restore back to my last successful updates. It probably would have been a quicker solution.  Any opinions or ideas would be appreciated.   Thank You  Sounds like you made the right choices. Good job! 
System Update Readiness Tool for Windows 7 for x64-based Systems (KB947821) [October 2014] Geek-9PM:  Thanks for your response. Do you think it was just a glitch and it is now OK to delete old Windows updates that Disk Cleanup discovers? Right now Disk Cleanup is showing me 70 MB of deletable old updates. And would it have been OK just to System Restore back to an earlier date hoping that the glitch might not recur.   Thanks again.Disc cleanup does not uninstall your updates. I'm not sure what happened, but you should feel free to allow it to delete everything it suggest - including sp1 files Quote

70 MB of deletable