I installed avast antivirus latest edition last week on win xp home edition. After which i am unable to open any win appln for ex IE, Control panel,regedit and i am unable to open the add or remove prog. i open ie by right clicking on it and click on run as and there is some security bar and uncheck it and then open. i found so many errors like unable to use the safely remove hardware when a usb is connected.
Then since i was not able to navigate to add or remove prog i clicked the installer of avast again and removed the antivirus thinking all these issues were related to it. Thought i would find solace after removing the avast but still the same situation.
now i installed a bootable win xp pro cd thinking i can format my c drive and install xp afresh but the error comes the hard disk is turned off and unable to continue with installation. but it boots into the hdd.

please provide me with a solution.
Thanks in advance

Maybe you should try changing setting s for Avast antivirus and disable some of the features?

If you can't get control of your PC, do this:

- prepare (if necessary) f6 driver floppy
- disable HD in BIOS <-- crucial
- boot with windows setup CD and install fresh copy. Formatting not necessary, although if you don't have any important stuff on your C drive - format it. Repairing windows might be better option.

Keep in mind that all of the software you have installed until now will only take up the HD space after repair/non-format installment of windows.

Also, when the first reboot occurs, change the BIOS settings and reenable HD and change booting sequence to start with HD.

I would like to know whether will i have to format the whole hdd. i mean i have some important stuff on other drives and i have removed avast too. i used the installer itself and i was given an option to remove and i did it.
And one more thing i tried booting with xp cd and tried a repair but got the same error.

if you mean you important stuff on other partitions of the same drive the answer is no just format the partition with winxp on it ,that is the reason we store important data on other partitions .

The error you get is probbably caused by lack of f6 drivers. CD that came with motherboard contains makedisk utility that makes f6 floppy you need to install windows.
Most of those CDs are bootable and you don't need an OS to produce that floppy.