hi,
my disk space is decreasing day by day all I do is just surf internet and run few programs.I don’t know wats going on.Is it registries prob or virus trouble…this also make my PC slow …it also showing some errors like “Access is denied”…need a solution or tool if any.??
Thanks. 
Oh, sorry, I was just assuming that you have the knowledge of all these things here…
Dude,
I think its a spyware in ur PC… & its affecting registries also… u should scan & delete spyware & also scan for distorted regs… & for this u can try Advanced System Optimizer…its tool System Protector helps u in scanning & deleting spyware & Registry Cleaner & Optimizer for cleaning distorted regs…try it… i m also using it for regular maintenance for my PC…!! It also contains some other useful cleaners & optimizers that can fix ur PC & increase its performance…!! dis is da best cleaning tool i used so far…!!
It is available at systweak site.
Yeah, I agree with you but the problem is we assume that the TS doesn’t have the technical skills for tweaking…
Well I assumed by the OP’s writing (and by their activities on the PC) that they weren’t in a position of knowing the technicalities involved.
So I recommended formatting as there’s no guarantees to the specific cause and a standard clean might not be worth the time spent (if it’s something bad).
You may take the first step by following xhtml and Crazybanana’s suggestions if it is still not working, try having regcure for your registry and if the problem persist, do AlexDawson’s suggestion starting from scratch…
I second that. If you’re inexperienced, whipping the drive and starting over is the best solution. The everyday PC user may run an anti-virus program or two that managed to pick up some of the mess, delete it… and think that everything’s gone. Chances are you missed something.
Clear all your temp files.
Download Malwarebytes Anti-Malware -> install -> update -> run. also run it from safe mode.
download CWShredder and run it. then download Spybot S&D -> update it and run it - also run it from safe mode.
if this doesnt help download Hijackthis and run it and look for suspicious entries. Dont delete things you are unsure of, if you are unsure, save logfile and come back and post it for people to have a look.
If you have a virus, just reformat and start from scratch… it sounds like your machine needs a good sweep-up anyway.
Going back to basics might be a good move for you, it’ll wipe out the virus and give you a “debris” free operating system.
The “Access Denied” sound like a web filtering program stopping you from surfing “mature” content. 
It may help if you check what programs you having running in the background and clear your temporary internet files, etc.