I have no idea why but I am now unable to logon to my windows 7 laptop.
I type in my password but the following message comes up:

The User Profile Service service failed the logon.
User profile can not be loaded.

How can I solve this?

ThanksBoot in safe mode.
Log into the Administrator.
Does that help any?Profile is corrupt from the sounds of it. You may have to perform a repair installation if the info geek provided doesnt help.

One other method that might solve this is if you had a Linux bootable disk with NTFS support to mount your HDD or SSD and you manually go in and delete this profile so that upon boot of Windows it has to create a new user profile since one does not exist.... *** I would copy this profile to an external drive PRIOR to deletion as for your pictures, videos, and all data in my documents as well as on the desktop will be gone when deleted and you will need to add these files back manually.

The safest method is a repair installation. If the safemode trick doesnt work.Thanks Geek.

I booted into Safe mode and it logged me in ok.
Should I delete the profiles and re-create them?It's F8 for safemode...tap repeatedly at powerup.Thanks Patio... any idea what I should do now?I booted into safe mode and logged in.
But then when I tried booting in normal mode I had the same problem.
What should I do once booted in safe mode?In safe mode you  create a new account with administrator level. You need that to repair the corrupt profile. This is documented on the MS website.
One you have the new user name, you reboot and select that user. Then go to the MS site and find the instructions.
This is for Windows 7.
http://windows.microsoft.com/en-us/windows/fix-corrupted-user-profile
read the instructions CAREFULLY.  Also, now is a good time to set a restore point. 
I've logged in with safe mode, gone to User Accounts, clicked on 'Manage another account' but nothing happens.
It won't let me create another account.
Any ideas?try enable your administrator account by typing secpol.msc then local policies click on administrator account then enable, restart & log into administrator account then try to create a account from that account...hope this helpcan you please explain how to do this in more detail please.
Where exactly do I type secpol.msc etcStart - RunAllan, I did that..
Clicked Start and then typed run in the area which says 'Search program's and files'
All that came up were 4 options
1. Run programs made for previous versions of Windows
2. View recommended actions to keep Windows running smoothly
3. Show which operating system your computer is running
4. View running processes with Task Manager
5. Review your computer's status and RESOLVE issues.

I also tried simply typing secpol.msc DIRECTLY into the white area but nothing happens.
I also tried typing cmd in the white area and when the command prompt came up I typed secpol.msc but I got a message 'is not recognised as an internal or external command.....'
you dont need to type run.. just type secpol.mscHwrddrn... Where exactly should I type run.
I typed in the white box after clicking start but a list came up (see previous POST)