Reboot with checkdisc

[Teabag]

HI, I have an Acer Aspire with win xp home. It has been trouble free for three years but now it keeps rebooting and then runs a checkdisc. Sometimes it finds something, sometimes nothing. It reboots if I plug anything into a USB port or the PCMCIA. and when I am loading software. I have checked in device manager and it says the ports are all working ok. I have even run the system recovery (from Acer) so the pc is back to 'out of the box' condition, with the C drive re-formatted etc. It still does it. I am also having problems installing some of the windows updates. It downloads them but fails to install them. Anyone got any ideas because I'm stumped.
Thanks
Teabag

[Teabag]

Hi ACtheTROLL and Ethel, Been fiddling all week with the dam thing, before I will take it in to the shop next week (�50 to look at it!). Read somewhere that it is sometimes a good idea to perform re-install of windows several times in a row when having probs like this. The laptop was getting much worse over the week, and I noticed that during chkdsk among the dozens of files it was correcting were a load of comodo av and firewall. Anyway I reloaded xp three times in a row and everything worked ok!!!. I nervously reloaded just vital progs and all is ok, USBs and pcmcia card work fine. I'm using zonealarm free and avast now and so far so good. Thanks for your advice, it's always good to know that there are folks who care about helping others, and I learned some new stuff along the way, cheers.
Teabag