Odd Start-Up Entries and Folders in XP Pro SP2

It seems as if my system has got infected but i am not sure about it, actually i have come across below entries in startup page.
when
I run "msconfig" in XP Pro SP2. I'll type them here under the three
headings shown in "msconfig"

STARTUP ITEM
default
ipconfig
IPCONGIG
NTUSER
ntuser
NTUSER.DAT
ntuser.dat
ntuser
NTUSER.tmp
ping

They were not there before, i have tried unchecking them but as soon as i restart my system after making the changes they appear again. I have checked out \pss of my system and below files are 1KB in size.
boot.ini.backuo
system.ini.backup
win.ini.backup

I have ran SpyBot a couple of times but its not detecting any infections as such. I think it is getting fooled by some virus.

It seems as if your main Startup folder in All Users\Start Menu\Programs\Startup has been deleted. If i am right than you will have to find out and replace it. You might have to do the same if individual user's Startup folder which is in User\Start Menu\Programs\Startup] might have got deleted. If you dont find main Startup folder missing than you can install some other recommended antivirus like Malwarebyte and run a complete scan.