Windows XP problem with a Dell 5100 laptop

[Falstaff]

was given a rather worn but operable Dell Inspiron 5100. It is running XPSP2 and all was well till my tech noticed that it had lots of rubbish on it, including a registry cleaner he couldnt identify as good. He removed all the crap and the Dell freebies from circa 2004 and rebooted the machine. Well BSOD and the error code is c000021A. I pulled out my old error code list and found out that with this particuler code I might well have corrupted registry keys or even renamed dll files, etc. Either way my tech isnt paid to work on my personal machine so he gave it back to me. I have tried to restore the machine but there is no restore partition, nor are there any disks. Just short of going into the repair console with a new version of windows what else can I do? It was working fine one moment and then now it cannot get past the error code whether I use F8 or not. I tried the Dell diagnostic and the hardware is fine, I really dont want to reload windows on this old machine but it would be great for just a mule or to fiddle with. Your expertise in this matter would be greatly appreciated.

[kn00tcn]

so you got some important files/rare programs on it that you dont want to lose?

when i have a failed OS, i just get a new hard drive & fresh install, keeping the old files on the previous drive

i havent done repair install off the xp cd (even when i switched mobos) but that may fix things & let you get back into the OS, with some/most programs & files in tact