Quick question, What do these mean in the logs?

[NotSoSavvy]

There is a regular visitor to my site, whose visits normally look like this:

24.xx.****.xx - - [0x/Apr/2004:0x:xx:xx -0x00] "GET /xxxxx/xxxxx.html HTTP/1.1" 200 40716 "http://www.xxxxx.com/header.html" "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; .NET CLR 1.0.3705)"

Suddenly, this same visitor's visits look like this:

24.xx.xxx.xx - - [0x/Apr/2004:0x:xx:xx -0x00] "GET /xxxxx/xxxxx.html HTTP/1.1" 200 40716 "http://www.xxxxx.com/header.html" "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; {C3A940AE-766D-4D2E-8631-8232D1290A42}; .NET CLR 1.0.3705)"

In other words, they are identical, except for the added {C3A940AE-766D-4D2E-8631-8232D1290A42}

Can anyone quickly tell me/direct me as to understand these?

Thanks in advance.

[sabrawv]

it looks like a clsid. for info, go to this link:
[w3.org...]