Learned Mr. Kameswarao has given valuable advice and has rightly pointed out "In general every company will store / capture the data in their main server and no employee can raise any objection for the same." And “no employee should use the company Information technology process for their personal use.”
It is not clear why there was a raid?
It is believed that you were not doing anything that could be detrimental to the decorum, business interest, and credibility, image of the company or anything illegal.
There have been instances of employees loading vulgar material. In such cases the employee does not deserve any opportunity and should be shunted out. In such an event if the line management/HR asks the employee to volunteer resignation and agrees to not to post adverse comments in relieving order/reference check , it is very reasonable of them and employee should exit without a blot on future employability. If asked employee may tender apology and pledge not to repeat in future.
There have been incidences of fake ID proofs being manufactured (in some cases under instructions/full knowledge of BM’s etc) using the features of various tools e.g. photo shop. Once the employee exhausted his social circle to fetch business for office the employee were coerced to resign or were terminated.
The access to a computer/intranet of the company, given to an employee is password protected. The access may be thru administrator implying administrator be able to also have the access. Employee may have the option/ right to change the password, on his/her own or thru local IT guy, but the administrator shall have the access/password.
In case of issues requiring defense/explanation employee can exercise his right to take out the print for use as enclosure. This may require approval as per email policy of the company, and the policy may or not be properly downloaded to the employees. However in case there exists a precedence that employer/custodian/line management harasses the employees and block the access for employee and jeopardize his right to defend and explain, with malafide intention to delay or tire and dump him, the employee may use his own wisdom and procure the records.
In your case since the access is password protected, and back up has been taken from the computer issued in your name and protected by your password and for which you are responsible, you should record your submission in this regard and you are within your rights to ask the reason and copy of material copied by legal cell. It seems that no notice has been given to you prior or later in writing. This may be a long exercise, however you can make note of all emails ( date, time ,subject, sender email id, recipient email id), folders/files, word excel, RAR etc....in al drives and submit it to your appointing authority and ask him to verify and supply you a verified copy. You can also raise the point even after taking the back up; company has not notified you and supplied you the copy/record. The point is that everything could have been copied in your presence as well and a list could have been given to you on the spot.
All said and done the legal cell is not like governor/DC appointed by law of the land who does not require giving any notice, or detail of record collected. If you are being taken for a ride with malifide intentions, you may prepare reliable fellow colleagues or even customers present to act as your witness, and defend yourself with all your might.
If you do not wish to post the facts you may consult elders in the family, competent and experienced well wishers and act with wisdom.An elederly advice may save from many losses and complications.