Install Important System Updates
1. Click the 'Start' button in Windows and expand the 'All Programs' folder. Click the 'Windows Update' link that appears in the first program column. This will launch Microsoft Internet Explorer.
2. Click the 'Express Install' button. Windows will begin searching for all important updates that you have yet to install, which will take a few minutes.

3. Click the 'Install Updates' button if Windows finds any important updates for your computer. The updates will begin downloading and installing immediately, but the process can take some time.
4. Reboot your computer when prompted to do so after the installation process concludes.
5. See if problems related to winhttp.dll still occur. If they do not, the updates likely fixed the problem, as updated versions of this file are included with most service pack updates for most versions of Windows. If you're still having problems, try the next section on restoring the last working version of winhttp.dll.
Restore the Last Working Version
6. Click the 'Start' button in Windows. Expand 'All Programs,' then 'Accessories' and then 'System Tools.' Click 'System Restore.'
7. Click the bubble next to 'Restore my computer to an earlier time' and then click the 'Next' button.
8. Select a restore point from the calendar by clicking on a bold date. If you just started experiencing problems suddenly, perhaps after installing conflicting software or getting a virus, choose a restore point from right before you started having problems. If you think the problem may have been there for some time, use the 'Back' button next to the calendar to scroll back to the earliest restore point. After you click a restore point, click the 'Next' button.
9. Read the restore details on the confirmation screen; then click the 'Next' or 'Finish' button. The computer will restore itself and reboot automatically, which may take several minutes.
10. Click 'OK' in the confirmation dialog box that appears after Windows starts up. See if you still have problems related to winhttp.dll. If you do, the best solution may be to replace the file manually. Find these instructions in the final section.
Replace Winhttp.dll Manually
11. Use your Web browser to navigate to a site where you can download winhttp.dll for free. You can find a link to a reliable download site in the Resources section.
12. Click the download link, save the file to your hard drive and open it. It will open in WinZip or your equivalent unzipping software. Unzip the winhttp.dll file to your desktop.
13. Double-click the 'My Computer' icon; then navigate to the system folder. If you're using Windows XP or Vista on a 64-bit system, this folder is at 'C:\Windows\SysWOW64.' If you're using either of those operating systems on a 32-bit system, the folder is at 'C:\Windows\System32.' In Windows NT and 2000, the folder is located at 'C:\WINNT\System32.' Finally, in Windows 95, 98 and Me, it's at 'C:\Windows\System.'
14. Drag the winhttp.dll file from the desktop into the system folder. If you see a prompt asking you whether or not you want to replace the existing file with the new one, click 'Yes.'
15. Restart Windows. Upon boot-up, Windows will register the new .dll file automatically, and you should be able to use Web- and network-related software normally.