When you upgrade to Windows XP, you receive:
rtl8139.sys is missing or corrupt.
To workaround this issue:
01. Close the error dialog or press Skip if prompted for the path.
02. After the upgrade is complete, browse the Windows XP CD-ROM and double-click the Driver.cab file in the I386 folder.
03. Select the Rtl8139.sys file and press CTRL+C to copy it to the clipboard.
04. Browse to the %SystemRoot%\System32\Drivers folder and press CTRL+V to paste the Rtl8139.sys file from the clipboard.
05. Right-click My Computer and press Properties.
06. Select the Hardware tab.
07. Press Device Manager.
08. Expand Network Adapters.
09. Right-click your network adapter and press Update Driver.
10. In the Hardware Update Wizard, select Install from a list or specific location and press Next.
11. Check Do not search. I will choose the driver to install and press Next.
12. Select you network adapter in the Network Adapter box and press Next.
13. Follow the on-screen instructions to complete the installation.