Windows XP explorer.exe corrupted

[laurelmlr]

I have a Lenovo T60 running XP SP2, with kaspersky Internet Security 2010 and antimalwarebytes. Kaspersky found Trojan.win32.packed.kl but can't seem to get rid of it. C:\windows\explorer.exe is infected. I have found a clean copy of explorer.exe in a backup folder. How can I replace the corrupt file with the clean one without reinstalling windows. Lenovo did not send me an XP CD. Thanks.