If you’re installing Windows XP Service Pack 2 and it halts or hangs on you while it is allegedly “Checking Product Key”, you can fix it like so:

1) Please go into the CMD prompt (Start/Run –> cmd.exe )

2) Then type cd /d %windir%\inf and make sure we are in that

3) Then type ren oem*.inf oem*.old, it will go back to the prompt
after giving you some error (Do not worry about it)

4) Then type ren oem*.pnf oem*.old1, it will go back to the prompt
after giving you some error (Do not worry about it)

5) Then goto start – run – type “%windir%\inf” and you will see
the files in the folder.

6) Then find the file by name INFCACHE.1 and take a backup of it
to desktop (by copying it to desktop) and delete the INFCACHE.1
from c:\windows\inf.

7) Close all windows and reboot the computer to safe mode and
start the installation of SP2 and it should go fine.

This solution is dotted all around the internet, but I can’t find it’s original source. If you know the source, let me know and I’ll credit it correctly.

Written by Phil Wiffen

Phil is an IT Professional working in Cambridge, England. He generally blogs about useful solutions that he comes across in his work/play.


ankit soni

sir i have a windows service pack 2 but when i install this sofwhere the computer genrets the eaorr that the product key is not valid and i chacke the key is sme as write on the cd what can i do sir

Hafiz Pussah

Hi Sir, I want to install window service pack 2 but i misplace the product key. how can are retrieve the product?


works like a charm…any reason to keep the “INFCACHE.1” file that was copied to the desktop?

Niraj Parmar

Hello Sir,

I have tried above trick but not working.
It still showing same error message “Your Product key is invalid.”.

Any clue?

Thanks in Advance.


Steve D

I have no INFCACHE.1 file. Should I just try the other steps?



Not working for me either. Performed all the steps, reboot to safe-mode, and launched the .exe and freezes at the same spot. Also completely reinstalled the OS and it’s still doing it. Any more advice?

I’ve seen this fix other places online so I’m sure it’s not a hoax. Just not working in my situation. Thanks in advance for any help.


Worked on my laptop. I formatted it twice and sp2 didn’t worked, then I followed your steps and it worked. Cheers.


Great Fix. Thanks for posting it in easy place to find… Messed around with it for long enough as it was.

Alex Huntington

Perfect, thanks for the help.

In regards to no INFCACHE.1 file make sure you have selected to unhide hidden files/folders & system files/folders

Should be located here:



Hi, this procedure worked on my laptop earlier.. but now after formatting and reinstalling the OS it is not working.. Somebody said ‘it’s hoax’… definitely not… it worked for me earlier.. but this time it is hanging at the same ‘Checking product key’ spot… any ideas??


Hey, the steps below worked for me:

the original instructions above didn’t work from me since i downloaded the sp2 pack and didn’t have the cd.

so you just modify the instructions…
1) start -> run -> cmd.exe
2) type %windir%\inf (folder will pop up)
3) find all the files in that folder named oem whatever (e.g. oem1.pnf, oem1.inf, oem2.pnf, oem2.inf, etc)
4) drag all of those files to your desktop (i had 38 of them)
5) find infcache.1 and drag to your desktop
6) reboot and your installation should finish (mine did)
7) replace all the files back to the %windir%\inf folder

install in normal mode only.. no need to go to safe mode…


Worked great for me too! I also had wasted several hours reloading XP and redownloading SP2 (just in case it corrupted in the download). You are my hero!


Its worked a treat, although as I was downloading the update from the web browser, once I followed the steps I ran the update again in normal mode and not safe mode and it worked ! cheers


Worked perfectly after reboot. I also ran in normally in windows. Thanks!


Umm…how are you installing it from Safe Mode? You cant go back to Windows Update in order to install it after this process?


Thanks Phil, I did the same thing Udai did and it worked great for my SP2 download from the website. Your fix was the only one that I found that worked!


brilliant – after what seems an eternity, i can finally install SP2 – thanks a million!


Just inputed what you instructed. Re-booted in safe mode. I had the sp2 file on my desk top but It didnt show in safe mode. I went to search option and found it. This is the best progress yet that I’ve made. Its still doing the update now but I never got this far before. I’ll post again once its done. 22.20pm gmt


Just popped out to the off licence and left the update running. Ive come back and just watched it successfully finish. 22.42pm gmt. My laptops restarted and all looks fine:)


Pete Austin

@Udai: Thanks, works fine! @Microsoft: Please fix your instructions – if you leave a situation where your official product can’t be patched, and fail to explain a workaround, you encourage people to pirate unofficial, but patched, copies of Windows.


Thanks! Finally got past that block. I missed the safe mode, and did a regular reboot, still worked.


thannks alot i had this problem for a while nothing worked so i tried your thread and it worked perfectly and easy to follow
thanks you again


My CMD keeps giving me the message “Invalid switch- /d”. I can’t even get passed this to continue. Please help?

Voytech Computers

Thanks Tons,

I am a fully certified Tech, and i found this blog, spent hours trying to get SP2 to install on an old HP Laptop that needed SP1 in order to accept the HP CD Key. It ran find in native mode, no need to restart in safe mode. Safe mode does not allow Service packs to install through a web browser so this method may irritate people. Other than that a perfect fix.

thanks again



WOOOOOO Hell Yeah thought I’d never get past that damn Product key bs worked great thanks alot Phil


Cheers great instuctions. thought my cd was scratched and downloaded the service pack and still got stopped at product key. wish i had googled it first could have used the data for something more usefull like a movie lol

Jimmy Mac

Tried to re-install XP after replacing a broken hard drive. Was tearing my hair out, but this fix worked a treat. No need to use safe mode, install worked straight away after following the instructions and rebooting normally. Cheers dude!

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