Many systems ship with them disabled in the BIOS. The first thing you should
do, however, is check in Device Manager. To do that, take these steps:
1. Click the Window button
2. In the search box type "compmgmt.msc" and hit enter
3. Click on "Device Manager"
4. If you see a Trusted Platforms Modules entry, expand it, right-click the
entry under it, select Properties, and verify the version. The computer must
have a TPM v.1.2 to use BitLocker with a TPM.
Assuming there is no Trusted Platforms Modules entry, restart the computer
and enter the BIOS (also called setup). Many computers ship with them
disabled. Dell, for instance, does. They are usually on the security tab in
the BIOS setup.
Dells Latitude Dx20 and Dx30 series all have a compatible TPM chip, and they
all have it turned off by default. Lenovo's Thinkpad T and X series also have
them, although Lenovo seems to treat it as the ugly stepchild they do their
best to ensure nobody knows about. HP has them too in some machines.
There is a great listing of computers with TPM chips in them at
http://www.wave.com/products/TPM_Matrix.html