Due to the nachia/welchia worm many ISP's are now filtering 92 byte icmp echo requests. Well it just happens NT uses a 92 byte icmp echo request to do traceroutes so this breaks tracert.

Here is a new version of tracert that will work, it uses smaller packets.

unzip it and put it in your system32 directory, then just type

tracert1 www.microsoft.com

and it will once again do what it is supposed to do.

I've had a couple requests asking how to edit tracert.exe. First it's a hex edit I'm
going to describe since as far as I know MS has never released the source.
Second, this is a procedure posted by one of the participants on news://news.barkto.com/homeless.nthelp
so if you have questions that's the place to ask.

The procedure is slightly different depending on whether it's NT4 or W2K, 

For NT4

Get yourself a hex editor (google is your friend)

Copy tracert.exe. In the copy, search for hex 6A 40 68 D0.
Assuming you find only one, the 40 is the length of the ICMP data (zero
filled). Hex 40 = 64.

Total ICMP packet length = 20 (IP) + 8 (ICMP) + 64 (data) = 92.

Change the 40 hex to 24 hex (dec 36). The changed tracert.exe now sends packets
that are 64 bytes = (20 + 8 + 36 = 64).

for W2K do the same thing except search for the hex string 6A 40 68 E0