winhttp.dll not found

Hi all, I have a bit of an issue.
A friend dropped off her computer and it keeps giving me a winhttp.dll not found on multiple programs when I try to run them. Lexmark lxmsdnmon and Microsoft's Fix It Center to name a few. I also can't get the windows update site to load, (just a blank screen), automatic updates don't work and if I go into services it shows Automatic Updates as always saying starting.
I can't get Add/Remove programs to load, (Blank screen).
I've checked and the file is there in system32 folder. I tried to replace the file but it won't let me it came up with a cylindric Redundacy failure. (don't know if I spelled that right.)
I ran sfc /scannow, it ran and just closed with no message if it fixed anything.
I've tried regsvr32 winhttp, but it says its not there.
I also did the regsvr32 jscript and vbscript and /i mshtml, with the last one giving me an error saying its already loaded.
None of this has worked.
I was going to do a repair on the system with the xp disc but after I boot up with it it just shows a partition but no Widows XP Professional there to repair.
I'm kind of at my wits end, I thought I would ask the experts before I do a reinstall of XP.
Any help would be appreciated.
Dave

It might be a good idea to run the manufacturer's hard drive diagnostics before doing anything else. If the hard drive has problems, it would be a waste of time to do a reinstall of Windows.

Good idea as "cyclic redundancy check" (CRC) error usually means some bad hard drive sector(s).

I too think you need to run the hard drive maker's diagnostic utility on that hard drive. Download this and burn it to CD, it has all the hard drive diagnostic utilities plus many more besides. You don't need to boot into Windows to run them, just boot up with the CD in the drive, select the utility that you want and it will run:

Ultimate Boot CD

If you aren't sure of the make of drive that is installed use the Seagate Seatools as it will work with any make of drive. You may find these instructions helpful for burning the UBCD .iso file to disc:

How can I write (burn) ISO files to CD or DVD?

So this is weird.
I ran DLG Hard drive checker for Western Digital.
It came back "No Errors"
However when I booted back into Windows, everything works now!
I can update and I don't get the winhttp.dll missing message anymore.
Did DLG fix the hard drive for me? But it said "No Errors" strange??
Anyways I'm doing updates now and we'll see what happens after I'm done.
One note: I started thinking it was a Net Framework problem so I ran the Framework clean up utility, which really just uninstalls them.
I had no errors after it finished and I started reinstalling the Framework files. I did 1.1 with no problem, but when I did 2.0 thats when the errors came back. I stopped after that. Then I ran the HD diag.
Anyways Thank You all and if I have a problem after the updates I'll let you know.
Dave

Some errors like you noted, can be fixed by the WD program. Might want to think about getting another hdd though. OI am sure you do not want to lose what you have now on your hdd.