I receive the following error message when trying to install QuickTime for Windows "Error writing to file C:/Program Files/QuickTime/QTSystems/QuickTimeCheck.ocx. Verify that you have access to that directory."

"Error writing to file C:/Program Files/QuickTime/QTSystems/QuickTimeCheck.ocx. Verify that you have access to that directory."

That one's consistent with disk/file damage. The first thing I'd try with that is running a disk check (chkdsk) over your C drive.

XP instructions in the following document: How to perform disk error checking in Windows XP

Select both Automatically fix file system errors and Scan for and attempt recovery of bad sectors, or use chkdsk /r (depending on which way you decide to go about doing this). You'll almost certainly have to schedule the chkdsk to run on startup. The scan should take quite a while ... if it quits after a few minutes or seconds, something's interfering with the scan.

Does the chkdsk find/repair any damage? If so, can you get an install to go through properly afterwards?

Yep, that what we'd have tried next. (Usual protocol is to rename the folder at least one level above the folder or file being complained about, because the issue may be with that folder rather than the file being mentioned.)

🙂 Glad you got things working again.