MTU fallen from 1458 to 1402

[#1]

While trying to diagnose another problem. I've noticed the maximum MTU on my connection has fallen from 1458 to 1402. I'm clueless as to why. Only change since I last checked is I've discontinued MAX Premium. Not sure why that would make a difference?
Any ideas.. seems like its cause a bit of a drop is download speed

Microsoft Windows XP [Version 5.1.2600]
(C) Copyright 1985-2001 Microsoft Corp.
C:\Documents and Settings\Andrew>ping -n 1 -l 1402 -f 212.159.13.50
Pinging 212.159.13.50 with 1402 bytes of data:
Reply from 212.159.13.50: bytes=1402 time=61ms TTL=60
Ping statistics for 212.159.13.50:
    Packets: Sent = 1, Received = 1, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 61ms, Maximum = 61ms, Average = 61ms
C:\Documents and Settings\Andrew>ping -n 1 -l 1404 -f 212.159.13.50
Pinging 212.159.13.50 with 1404 bytes of data:
Packet needs to be fragmented but DF set.
Ping statistics for 212.159.13.50:
    Packets: Sent = 1, Received = 0, Lost = 1 (100% loss),
C:\Documents and Settings\Andrew>ping -n 1 -l 1402 -f www.google.co.uk
Pinging www.l.google.com [216.239.59.99] with 1402 bytes of data:
Reply from 216.239.59.99: bytes=56 (sent 1402) time=71ms TTL=245
Ping statistics for 216.239.59.99:
    Packets: Sent = 1, Received = 1, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 71ms, Maximum = 71ms, Average = 71ms
C:\Documents and Settings\Andrew>ping -n 1 -l 1404 -f www.google.co.uk
Pinging www.l.google.com [216.239.59.99] with 1404 bytes of data:
Packet needs to be fragmented but DF set.
Ping statistics for 216.239.59.99:
    Packets: Sent = 1, Received = 0, Lost = 1 (100% loss),
C:\Documents and Settings\Andrew>

[#2]

Has the MTU on the router changed? You are measuring from your pc to google so its the MTU of the pc you are measuring. The router has an MTU as well and this effects your mtu as you are going via the router.
What you are measuring is a snapshot in time to get a better picture you need to try the same test at other times of the day and over a week to see if its consent or just down to traffic

[#3]

Your tests show that your PC's MTU is 1402+28=1430.  However, this could be related to the MTU setting at your router.

[#4]

Must admit I'd forgot to include the IP header 
Checking my Router its 1458 at the moment.
Ah ha! Mystery solved! Looks like the network card on this machine has an MTU of 1430 unlike my other machine that I used to configure my Router that is 1458.