Unable to Install XP SP1

>-----Original Message-----
>Background:
>Got in big troubles trying to reinstall a version of MSN
>Messenger to fix a problems sharing viewing others PC
>camera image.
>
>MSN Messenger upgrade turn out in installation
>compatibity issue between the Version of MSN and XP.
>Obtain correct version and the sw installs, but I never
>connect to MSN services due to an invalid user/pwd.
>
>Moreover, now I cannot read hotmail messages using the
>Internet Explorer due the same reasons: unable to
connect
>MSN service because the user/id does not exists.
>
>Well, that only happens on this particular XP computer
>since I can connect well through other PCs with MSN
>Explorer/Messenger.
>
>Recovery Actions tryied:
>Attempt to install for first time Windows XP sp1,
without
>any success.
>
>"Setup could not verify the integrity of the file
>Update.inf. Make sure the Cryptographic service is
>running on this computer."
>
>And guest what, the service is running: svchost.exe.
>
>Please help...
>
>.
>