I have used memtest86 on many computer including my T60 and my R61 without any problems. I did encounter one odd thing with an IBM Netvista computer. I ram memtest on 7 identical computers and they all showed memory failures within just a few minutes of starting memtest. Changing memory did not help. I think memtest did not like those specific motherboards.
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T60 2623-D7U, 3 GB Ram. Dual boot XP and Linux Mint.
T400 2765-T7U Windows 7
Registered Linux User #160145
FYI: I am not employed by Lenovo