Computer question

OK, so every now and then when I start up my computer it goes as far as the windows XP page and no further, so I shut it down and start again. So far it's always started the second time, but i have to reset the clock etc etc. Any ideas what might be wrong with the bloody thing? The CPU is probably 2.5 years old and the hard drive is just over a year old.
Cheers

Usually if your clock resets itself, then your CMOS battery needs to be changed.
Somewhere on the motherboard is a small silver battery the size of 50c. Usually a CR2032.
If you are competent, get it out and test it. If necessary, change it. Otherwise get a 14yr old expert to do it.
May or may not be the cause of the problem.

So that would cause the computer not to complete start up?
Cheers