Lockup/freeze After Boot?

I have a Samsung chronos 7 running windows 7x64, a few months old, and as of yesterday it has developed a problem. It boots up and I can login as quickly and effortlessly as normal, but after a short while, 30 secs to a minute after, the whole machine becomes unresponsive and incredibly slow.it cant even open windows such as "my computer", and cannot shut down, i have to force a shutdown with the power button.I noticed after a couple of reboots with that happening that when it freezes the hard drive activity light is solidly on, as if the drive is in constant use.At this point I attempted to run chkdsk as soon as i logged in, trying to beat the lockup. It crawled to 67%, stage 2 verifying indexes, 329020 of 361216 processed. At that point it froze for hours.I reset and booted into safe mode and ran chkdsk again. This time it sped through to 67% again, even the same index number and froze.In safe mode the computer was useable slightly longer before it froze and chkdsk ran faster but same result, no response, light solidly on and its now been there for 7 hours on 67%, whearas reaching that point took about 5 seconds.Also accessing logs may be a problem as i only have my phone to get on the internet with, but if theyre small files i may be able to upload them from here.I really dont wanna have to replace the drive or reinstall windows as my backup external drive died last week and I haven't got the money to buy a new one at the moment, so i have no backups of my laptop or facility to make one, so thats a last resort. Also running any programs is an issue because of the 30 sec winfow before it locks up.