Thanks to pratham. The Impact cable problem has been solved

The IMPACT Cable problem has been solved.

A regular USB cable is connecting the PC with Spartan-3E Starter Kit.

The initial status from Device Manager is as follows.

Jungo's WinDriver: C:\Windows\System32\Drivers\windrvr6.sys (192 KB, version 10.2.1.0, dated 2010/8/31).

Xilinx USB Cable is located on 0 (Port_#0004, Hub_#0001)
Attempt I

1. Disconnect USB cable.

2. Run C:\Xilinx\14.7\ISE_DE\ISE\bin\nt>wereg -compat -inf %cd%\windrvr6.inf uninstall

3. Run C:\Xilinx\14.7\ISE_DE\ISE\bin\nt>wereg -compat -inf %cd%\windrvr6.inf install

4. Reconnect USB cable

5. Run Cable Auto-connect and the following is shown in Console window:

Checking cable driver.

Driver windrvr6.sys version = 10.2.1.0.PROGRESS_END - End Operation.

Elapsed time = 2 sec.

Cable autodetection failed.

No connection between PC and Spartan-3E board.
Attempt II

1. Deleted windrvr6.sys from C:\Windows\System32\Drivers\

2. Disconnect USB cable.

3. Run C:\Xilinx\14.7\ISE_DE\ISE\bin\nt>wereg -compat -inf %cd%\windrvr6.inf install

4. Check the reinstalled C:\Windows\System32\Drivers\windrvr6.sys. Its property is still "192 KB, version 10.2.1.0, dated 2010/8/31"

5. Reconnect USB cable

6. Run Cable Auto-connect and the following is shown in Console window:

GUI --- Auto connect to cable...

INFO:iMPACT - Digilent Plugin: Plugin Version: 2.4.4

INFO:iMPACT - Digilent Plugin: no JTAG device was found.

AutoDetecting cable. Please wait.

*** WARNING ***: When port is set to auto detect mode, cable speed is set to default 6 MHz regardless of explicit arguments supplied for setting the baud rates

PROGRESS_START - Starting Operation.

Connecting to cable (Usb Port - USB21).

Checking cable driver.

Driver file xusb_emb.sys found.

Driver version: src=1029, dest=1029.

Driver windrvr6.sys version = 10.2.1.0. WinDriver v10.21 Jungo (c) 1997 - 2010 Build Date: Aug 31 2010 X86 32bit SYS 14:35:41, version = 1021.

Cable PID = 0008.

Max current requested during enumeration is 74 mA.

Type = 0x0004.

Cable Type = 3, Revision = 0.

Setting cable speed to 6 MHz.

Cable connection established.

Firmware version = 1029.

File version of C:/Xilinx/14.7/ISE_DS/ISE/data/xusb_xlp.hex = 1303.

Firmware hex file version = 1303.

Downloading C:/Xilinx/14.7/ISE_DS/ISE/data/xusb_xlp.hex.

Downloaded firmware version = 1303.

PLD file version = 0012h.

PLD version = 0012h.

PROGRESS_END - End Operation.

Elapsed time = 1 sec.

Type = 0x0004.

ESN device is not available for this cable.

Connection between PC and Spartan-3E board has been established.