How to resolve DllRegisterServer error when registering an OCX component?

I have to fix a computer running Windows XP SP3, which has accumulated a fair amount of company-specific software, meaning that OS reinstall is not really an option.

The thing is, I need to install a package named MetaWeb. When I run the installer, it goes on until the "Registering modules" part, where it stops saying:

MetaWebURL.ocx failed to register. HRESULT -2147220991.
Contact your support personnel.

What I have checked:

1. I run the installer as Administrator
2. There is sufficient space on drive C: where I install the package.
3. My system meets minimum system requirements for the package (WinXP + IE 7-11, I have IE7 installed)
4. Registering manually with regsvr32.exe MetaWebURL.ocx fails with the same code (0x80040201)
5. Running regsvr32.exe /u MetaWebURL.ocx completes DllUnregisterServer successfully
6. My % Registry Quota In Use is below 50%
7. MetaWeb is not the only package that fails to install on this system: video driver update (Intel HD Graphics) fails right after the "Copying files" phase, saying that system resources were not sufficient to install the driver.
8. My user has full access to all four branches of the registry (HKCR, HKCU, HKLM, HKCC). I have also checked several sub-branches, including HKCR\CLSID.

I would appreciate any pointers which help to better understand the cause of these issues.

Use Dependency Walker to find any missing referenced dlls with which this OCX file is linked.