Installed Program disappearing and Installshield errors when trying to install...

Hello, been having some problems with installing POL (Playonline Viewer) and FFXI (Final Fantasy 11... MMORPG) over the last few days... here is the scoop:

I reformatted my PC (several times), installed sound drivers, installed AOL, and I go to install POL.. it installs fine (I even see that it is being registered at the end of the install), I then check it out in Add/Remove programs, and it is there...
So then I continue to install FFXI... I go through the first 3 CDs (the 4th CD is the Rise of the Zilart expansion) and see that it registers the game at the end of THAT install (I check Add/Remove programs yet again, and it is there). I then put in the 4th CD and install it.. I see the register, and then I go to install the Chains of Promathia pack... and the computer lets me know that FFXI is not installed and I should install it first... (which I have just done) (and the POL and FFXI entries in the Add/Remove programs are GONE at this point) (also the files that were installed are still on my other HDD, but I am guessing the registry entries arent in the registry, and that is making the PC think the game arent installed... but what would cause it to do that?)

So when I put CD1 of FFXI back in it tells me that POL needs to be installed first... which it was but for some odd reason it isnt installed NOW... so I go back and click on the POL shortcut and it tells me, "Error code = 20008014 Cannot open registry key for install path of Playonline-compatible software ID=1000"

So I try it again, and it does the same thing...

At one point I was actually getting a Installshield errors too... where it woudn't even try to install it...

I have WinXP w/SP1 (had SP2 but it was giving me hell too), GeForce ti 4400 video card, 1GB RAM, 2700+ Athlon (or somewhere around that)... two HDDS... one HDD for WinXP/programs/Windows, and one HDD for FFXI/POL/files/mp3s/etc (hasnt been reformatted recently) ... newly reformatted Window's HDD (several times) ... did quick format and slow/tedious format... NTFS (not FAT)... NOTHING is on the PC that shouldnt be there except maybe AOL (I only say this because AOL is the only other thing on it)...

Is there a virus that will do something like that? Could it have infected my other HDD and somehow linking with FFXI when I try to install it?

ANY help would be appreciated.

(btw... POL is the program that is needed by FFXI in order to get "into" FFXI... almost like a stepping stone... you cant run FFXI without POL)

 

I am not sure if it is fixed or not, but I bought a new HDD (the Windows HDD I was using was an old 7GB HDD back from 1996 or so...

and I didnt install the AOL 9.0 Security Edition... (which I was thinking might have been acting like a registry safeguard and not keeping newly installed programs on the registry... or something )

So far everything seems to be ok...

for the time being...