I have a Time 7321 laptop and when i switch it on it comes on for a few seconds then it just switches itself off. I have tried booting up through the mains but still no luck i have changed the internal battery but still no luck and i have tried with no cd ar floppy drives to no aveil. I'm slowly running out of idea so any would be very much apreciated the laptop is only 18 months old.

Is the computer still under warrenty? If it is I suggest contacting the company that you got it from.

no warranty has run out

That's normally a symptom of the computer's microcontroller detecting a problem with a hardware device during it's early startup diagnostic & configuration process. Here are a few (there aren't many things you can try with a laptop) things I'd try:
1. Remove and reseat the RAM - try a known good stick of RAM also if the reseating doesn't work.
2. Remove the hard drive and any "plug-in" devices such as the FDD, CD unit, PCMCIA card, etc and try starting the computer without any of these attached.
3. Remove the CMOS battery (this is the small one on the motherboard, not your main power battery) and let the computer sit that way for a couple of hours, then install a new battery and try it.

I'd suspect a RAM or HD problem, but because it's "ON" time is so short, it could also be a CPU problem (can't change this on most laptops).