I have Ubuntu running alongside windows 7. When Ubuntu starts it almost immediately freezes, requiring reboot for the same each time. Windows works OK.

What happens when it freezes, what is displaying on the screen

the screen freezes where it is, and the cursor won't move.----------------------------------------------------------------------------------
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> Subject: Re: [Question #204475]: I have Ubuntu running alongside windows 7. When Ubuntu starts it almost immediately freezes, requiring reboot for the same each time. Windows works OK.
> Date: Sun, 29 Jul 2012 11:26:00 +0000
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> Your question #204475 on Ubuntu changed:
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> Status: Open => Needs information
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> samuel requested more information:
> What happens when it freezes, what is displaying on the screen
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Have you tried the Unity2D session?

No, what's that ?

When you log in, click the Ubuntu icon near your user name and select the Unity2D session, then log in. Is it better there?

Thanks. I did that as suggested. The two options were Ubuntu and Ubuntu 2D. I tried both and it made no difference.
The laptop froze again within 20/30 seconds.

Have you tested the RAM using memtest in Grub?

No ! How please ?

It's on the same screen as when you select between the OSes

I can't do anything in Ubuntu as it freezes as soon as it starts.

No. All it says on that screen is 'Tools: windows memory diagnostics', which I tried with no effect.

It's also on the install CD.

Unfortunately no CD ! I installed using the Windows installer as the laptop has no DVD/CD, and it wouldn't let me use a memory stick, as it said I could. One benefit of the dual operating system is that the computer still operates happily in Windows. Thanks for your efforts so far, I'd appreciate any further advice to beat it. I have another laptop (Sony Vaio) and the two systems work OK on it. The laptop that is playing up is a Acer Aspire One 722, is that significant ?

What release are you installing. Apparently this model has a problem with freezing due to the wireless adaptor but that's supposed to be fixed in 12.04: http://delightlylinux.wordpress.com/2012/05/02/ubuntu-12-04-and-the-aspire-one-722/

Also, don't power off when it's frozen unless you've already tried Alt+SysRq R-E-I-S-U-B (http://en.wikipedia.org/wiki/Magic_SysRq_key#Uses)

I'm using 12.04, Asus Transformer TF300T only a couple of months old. I'm trying your suggestions above but still not fixing the fault of freezing almost immediately starting up.