[z8saa]

I had a trojan removed from my system recently along with copy.exe file. I cannot open the drives as it shows the error copy.exe file not found

[Curlyben]

First try a system restore to a date BEFORE the trojan.
Failing that my maintenance steps should help as it sounds like there's more going on then you know.

The last step, repair install, maybe the best course of action, but do everything else first.
Here's my usual C&P for cases like this:

When was the last time you did some serious maintenance on your system ?

System maintenance includes:
Defrag
FULL patching
Virus scanning
Spyware scanning
removal of rubish files

Defrag is an inbuilt function in XP.
Open My Computer > Right click C: > Tools Tab and its there.

To make sure everything is running fine run both anti virus and anti spyware apps in normal AND safe modes. (make sure that they are updated first ! ;)) (AVG is good and free AV)
(A couple of good removal tools are Spybot and Adaware)

ALso an on line virus and spyware scanner is Trend Housecall

Just a note; actively running two AV's on one machine can cause problems.
So if you are thinking about it make sure your current one is disabled first.
Same thing applies to online scanners as well.

Removal of junk files is easy with CCleaner a free app that does exactly what

If all this fails then a repair install may be in order:

Here's the official Micro$oft way of doing it,
and Here's one with screen shots.

Basically this installs windows over the top of your current setup.
So you don't loose any information you already have.

This lot should resolve your issue.