I have an old PC (PII, 500), originally had 98 on it, but wanted to network with my other PCs in the house, so I recently loaded 2000 Windows and Office.  All was fine (as a standalone, not networked) until I loaded McAfee Suite on it and all of the sudden started getting fatal errors anytime I went into I-Explore.  I unloaded the McAffee and it improved some but still got intermittent IExplore errors.  No errors when offline but after varying amounts of time on-line, I will eventually get an error and it either closes Explorer or reboots completely.  Out of desperation, I tried installing XP today and all sorts of new trouble started.  XP INSTALL failed due to numerous "Can't find such-and-such...."errors and now is locked in a continuous loop of "Can't find Command.com" and FORCES reboot.  Nothing I have been able to do with my old 2K Restore disk or XP Install disk gets me past this.  I am willing to reformat the HD and completely start over but can't get to a DOS command.  Any thoughts as to how to get passed it's desire to finish the aborted XP Install?  Is there a bootable disk I can download on-line (using another PC) that will allow me to reformat everything and start fresh?  Any help would be appreciated.  BTW - the PC is a no-name and I have no documentation for it.  Thanks...JHBoth the Win2K and the XPCD's should be bootable...make sure to enable the CDRom as the first BOOT device.
Then in setup you should have the option to delete any existing partitions and re-create them and do a clean install...Thanks - but done that.  It only comes up as far as telling me it cannot find Command.com, regardless of which device I have forced it to look at.  I have even tried forcing it to my floppy, using an older restore disk for 98 - just to see if it does anything different, it reads it but then errors out saying it can't find the required file.  The only screen it consistently comes to is something to the effect that it failed install, can't find the necessary file, install orignal disk and press "r" to repair.  I put in the XP disk press "r" (or anything else) and it reboots and comes right back to that same screen - endless loop and no apparent way around it.  I have shut down my HD's to ensure it forces a read off the CDROM and/ or floppy, but same result.

I am getting a LITTLE foggy on some of the screens so if thee is something spcific to try, I can certianly give it a go.  Thanks again.  p.s. - would buying a new HD and starting from scratch get around this?Well, I  might have been a bit premature.  I was able to get the Win2K disk to read and got into the repair option.  I am CHOOSING to reformat the HD and will start over - hopefully whatever it was that got introduced with the McAffee suite will be wiped out and I can get back to where I started - just a lot of time to go through getting all the updates again.  Thanks for the help and if things don't go as planned, I'll probably ask a few more ??No problem ...let us know how it goes...
For a full Protection strategy here is mine:

AVG Free
Spybot Search and Destroy
AdAware
AVG Anti-Spyware
Stinger
CCleaner

All of the above are FREE and will not bog down the system as some of the "Protection" Suites will.

Many here also recommend Comodo for a free firewall program to round out the package.

Good Luck and Welcome to CH !