i think that would not work.
first you need the boot files and config made to boot from disk C: or your xp will never boot (as my guide explains must be done of a cluster size of 4k = 4096 bytes)
also any file compressed on the image partition once put on the new 64k cluster size the os will not be able to read it. since the os shuts down the support for file compression on the partition with a cluster size of 64k.
plus your windows uses the letter C: as the partition holding the xp installation and since that would not be the letter anymore would permanently damage the os.
in a big resume, no you cant.
wait untill your xp crashes gets damaged etc. then do a clean install.
i will not recommend under any circunstance to do this kind of experiments specially on a fully working windows xp installation thats not damaged.
this is a guide if you buy a pc or you are about to do a clean install of windows to make it as fast as can be. specially because windows will not compress any files without permission as it uses to do (the folder dllcache that its a secure location where the system files are copied as a backup, unistall folders etc).
plus the paging file will be read alot more faster than normal.
here i leave you screenshots of benchmarks of my hard disks. all my hard disks and usb flash drives (pendrives as you wanna call it) are formatted with NTFS with a cluster size of 64k. i did not test the C: drive because its just 15 mbs and its used 9 mbs. plus the minimum for the scan is 50 mbs.
this is my real pc not a virtual one.
i must say that the speed has many variables: your processor your ram your motherboard your operating system your hard disks, etc
that means that yes it will speed all up but dont expect to do this on an old pc with a old IDE disk and have the speed of a SATA II disk.
all my disks are SATAII (except the flash disks that are A: and B: and are usb 2.0) and are optimized even the firmware internal options (i jsut buy a hitachi disk that its the E: one and the site has a nice utility to change settings like work on 48 bit enable disable smart, the SATA link to use be SATA 1 or 2 mode, etc my 2 other samsung drives a similar utility also and configured)
also in windows 7 was almoust twice as fast than in xp, also because my windows 7 was also working on 64k and that works on 64 bit contrary to my current xp working on 32 bit.
anyways here the screenshots: (you just take into consideration the line that has a green button that says seq. = sequential test or normal test we can say) working with a 100 mbs file)
disk A: (flash disk usb HP v100w 4 gbs of capacity usb 2.0) :

disk B: (flash disk usb HP v100w 2 gbs of capacity usb 2.0) :

disk D: (samsung HD161HJ - primary - SATA II - 160 gbs of capacity) :

disk E: (hitachi HDS72150CLA362 - secondary - SATA II - 500 gbs of capacity) :

disk F: (samsung HD161HJ - secondary - SATA II - 160 gbs of capacity) :

NOTE: i have 2 physical disks samsung same model and yes they have pins as IDE disks for primary and secondary even beeing SATA II they are rare i guess lol.
as you see are high speed (specially the D: partition that with my method its holding the OS).
i have found a way so you dont need windows vista-7 repair disk;
install partition magic 8 (or later aldo the 8 version i think its the final one) delete the current partitions of the desired disk to install 2000-xp (this can be done booting from the booting diskettes you can do or from windows 2000-xp!) create 2 new partitions: first at the begening of the disk and set as active and primary, 15 mbs formatted with NTFS with a cluster size of 4096 (4 k)
the rest of the disk or the number of partitions that you desire, but its better if its the D: partition used for windows, formatted with NTFS with a cluster size of 64k (if you do other partitions you should format the same as the D: one)
apply the changes. (only on windows) it will ask a reboot to apply the changes.
it will do a boot execute (like when you run disk check and you need to reboot) it will do all since the program uploads itself to the ram. once all its done, you just need to reboot the pc with the windows 2000-xp setup and continue from my guide point, choosing the correct partition and then select "leave the current system file intact <no changes>" and done.
WARNING: if you use the windows option, you will lose all the data on your disk including the windows you use to do the formats!!!
again, this is for new computers or computers with a damaged beyond repair windows 2000-xp.
do not experiment.
if you want to keep your current windows, with partition magic you can make smaller the current partition to leave space for another one. (WARNING: this may damage the partition while it makes it smaller, may damage the MBR leaving the current disk raw while you lose all data in the disk. do it under your complete resposability this experimental option)
or even on another disk that its not set on bios or with a pin as primary.
just do one partition (in another disk its preferred or in the space left after you make smaller the partition, btw partition magic on windows will ask a reboot for that) with NTFS with a cluster size of 64k.
if you have xp you can install another xp version. NOT windows 2000 or windows xp will not boot anymore.
if you have 2000 you CAN install windows xp on the partition with 64k.
again this experimental secondary bypass of my method its UNDER any circunstance recommended by me. use only for example (if you use the bootable version of partition magic, also known as norton partition magic or manager dont remember) if you have valuable data or documents on your pc and you dont know or cant connect the disk to another pc and extract the non backed up valuable data.
but again this part i leave it as a experimental method if you have for example an old pc that does not have NO valuable data and you feel with the experimetal fever. in other way DONT do it.
again i dont assume any responsability for damage on your data if anyone try this experimental method.
also i put it here since any intermediate-advanced computer skilled person can figure this out. i do it to make sure if you try this insanity (refering only to this bypass of my method) you do it without loosing your MBR partition table or even valuable not backed up data.