Thank you carbon_unit.
Summary:
Original problem: Not able to boot or access data into a 40GB HD with three partitions a --> OS, b --> Files-Music, c --> Photos.
Possible reason: MBR table corrupted after attempt of resizing the partitions to get more space allocated into the OS’ partition. I’m guessing because of the size of the OS partition was too small, so something went wrong when the partition software (Partition Commander) tried to resize the partitions.
Status: solved in a 95%. Files and data copied to an external HD. OS’ partition never work well again, so a “clone” install was performed from a 120GB HD using Acronis True Image Workstation version.
Solutions:
1. PC Inspector recovery software: easy interface, reliable, and free. Caveat: I wasn’t able to copy more than one folder at the time, it crashed.
2. testdisk: not that straight forward, but not difficult after a bit of reading and trying. Free as well. I solved 95% the problem: Partitions “b” and “c” were accessible and I was able to copy everything that was in them to an external HD.
3. Easy Recovery Pro: Files got grouped into extensions, for example all *.jpgs in a folder, *.doc in a folder, etc. Also, free evaluation version doesn’t allow you to save, so it is pointless.
4. miniPE: It’s a kind of Live Windows autoboot CD. I has many tools in it, and it’s for sure a CD you want to have in your shelf in case something nasty happen to your system (Windows XP). Didn’t help too much in this case because the problem was already solve in a 95% by testdisk.
5. Windows XP OEM disk: It may help to get into Windows Repair mode/console.
6. Acronis True Image Workstation version: very easy to work with, and excellent tool. Free version is fully functional for 15 days.
Lessons learned:
1. This might be obvious for many, but in any case: I consider a very good practice to have you HD partitioned in at leas two partitions: One for the OS, and one for all your documents, photos, etc. In case you have a system crash, the chances of getting back you data are increased a little bit.
2. Do regular back ups. I did manage to copy everything back after all from partitions “b” and “c”, but I technically didn’t have to because I have previous versions of many files backed up into an external HD. So regular back ups are very good.
3. Always have an OEM Windows XP CD, or as I explained, miniPE type of CD in case something goes really bad.
Ok, this is what I did:
1. I re-scan the 40GB HD using PC Inspector. Again, it took about 1h. I copy folder by folder what I consider the data I need. Took quite long time, but it worked OK.
2. I thought to give a try with other methods suggested here or in previous posts. After all, I recovered the most important data I need, so nothing worst would happen. I started with testdisk: it's not a straight forward application, but with a little bit of time and patience, it can be easy to work with. After working with it, I'm very happy to report that I was able to fix the MBR (well, partially) so I could see again the three partitions: a--> OS, b --> Files, music, c --> pictures. Perfectly, with no errors. When I say that I was able to "see" them, I'm talking about having the 40GB HD attached by the USB caddy to the laptop, and have them recognized by Windows. When I tried to access partition "a", I got a Windows message "Disk with not format, would you like to format now?"; but partitions "b" and "c" where not problem at all, therefore, fully copied them to another external 300GB Maxtor HD. I can tell you all, I was very happy. At this point, I considered this battle won by 95%.
3. After having the files secured, I tried to get back to work the OS in partition "a". I took the 40GB HD off the caddy, and installed back to the laptop. When I rebooted it, I got a "NTLDR missing" message after the BIOS booted. I searched for this message, and I tried solutions like copying the "\i386\ntldr" and "\i386\ntdetect.com\" files back to the "\i386\" folder, but that didn't work.
4. Then, I also tried miniPE, a "live Windows 'autoboot'" CD. For those of you interested, google it and you'll find lots of info. It was suggested here in another post. I tried different tools there, but not luck.
5. Next was to boot into Windows XP repair mode with an OEM Windows XP CD I've at home. I entered, and run fixmbr and fixboot per suggestions here in another post. Well, it was after this that things got worst. It didn’t boot: gave the Windows XP first screen, and then a very weird blue screen with error messages. Also, after I put back the 40GB HD into the external USB enclosure, and put in the 120GB HD into the laptop, the "a" partition was not longer recognized by the system. It got a "RAW" classification. I tried many things with testdisk, but not luck.
6. After trying back and forth with the 40GB HD in and out of the laptop, I got tired and since I already got the files out of partitions "b" and "c", I decided to get rid off the OS, and clone the 120GB HD back to the 40GB HD. Yes, I know it sounds weird, but I didn't want to go again through the process of clean installing the OS into the 40GB HD since I did it once into the 120GB HD. I got Acronis True Image Workstation version, and clone the 120GB HD into the 40GB HD. I have the 120GB HD partitioned in three drives: OS, files-music, photos. I thought that I'll be able to install the 120GB HD OS partition into the 40GB HD "a" partition, or the whole 40GB HD space, but as it turns out, you have to clone exactly what is in the base HD. It asked me that the 40GB HD need to be re-format, so not problem. Very easy process to do with Acronis, so not problems here. Didn't take to long, and at the end, I have my 40GB HD back to work!
Thank you all

,
K.