XP taking huge drive space

I have XP in drive C. But I am looking it is automatically taking huge space and reducing the space size day by day. I have checked al the file size throghly but that does not match with total size of the drive (that mean acquired file size in drive is lower than total space acquired). That mean some invisible file or program is taking space in my drive. I have McAfee Antivirus updated and sure that it is not happening with any virus. Can anybody tell me what's the reason behind it and how can I solve it?

Where exactly are you getting this information? Disk Management?

Drive C: will hold not only XP but all installed programs unless you have directed them to other drives.

Still the registry is on C: and will generally increase in size. Plus all XP updates. 4 to 6 GB is normal for XP SP2 itself.

Do you Defragment your hard drive?

Yes, I am getting the information through Disk Management
I know there are several software applications in C, but I have note down file sizes of all the softwares and finally calculation is not matching with the needed blank space and acquired drive space.
I dont do any kind of update in XP. But it is gradually taking the space day by day where I am not finding the file which is taking this size.
Though I have not defrafmented the drive till now.

Defragmenting is good to do. Start > All Programs > Accessories > System Tools > Defragment

You should also take all Critical Windows Updates via start > All Programs > Windows Update

XP will also employ the hard drive for memory space if and when it needs it.

What is the size of this drive?

How much RAM do you have?

The less the RAM (especially under 256) the more XP will draw on your hard drive.



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Here are some links on freeing up space and also defragmenting
http://pcworld.about.com/magazine/2007p162id97442.htm
http://www.pctechguide.com/tutorials/HDDMaint.htm#Scope